mow I s ® 



m\ A 




Class 
Book 




3^25 



V<£ 



OopigtaN . 



COPYRIGHT DEPOSIT. 



H@W TO 
P MS> 1>1=S TAMP 

i/i& Reading of 

BLOB PMMT 





^ 



THE FUNDAMENTAL PRINCIPLES SIMPLY EXPLAINED 

BY 

EDWARD R. VIGNEAU, I. E. 

Author of Theory of Operation, Vaporization, Ignition Care and 
Management of Two-Cycle Gasoline Engines. 

Member of Detroit Engineering Society. 



228 ILLUSTRATIONS 

AH illustrations made by the author. 



PRICE $2.00 



PUBLISHED BY 

EDUCATIONAL INSTITUTE 

100 ROWLAND BLDC. DETROIT, MICHICAN. 






Title and Cover Design Registered 

U. S. Patent Office 

and Contents 



COPYRIGHT BY 

EDWARD R. VIGNEAU 
1919 



ALL 

BRITISH 

RIGHTS 

RESERVED. 



1A515046 



■ / \^JO \ 



CONTENTS 

PART I 

THE ELEMENTS OF BLUE PRINT DRAWINGS 

PAGE 

Introduction 5 

Perspective Drawings 7 

Dotted Lines 8 

Full Lines 8 

Plane 9 

Views 9 

PART II 

ELEVATIONS 

Straight View Proj ection 10 

Another Method of Straight View Projection 21 

Third Method of Straight View Projection 26 

Projecting to a Plane what Lies Back of a Plane 32 

Proj ecting of Lines and Points 35 

Examples of View Proj ections 46 

Information that One View Offers Another 50 

PART III 

Distinction Between Views, Elevations and Plans 50 

PART IV 

DIFFERENT NUMBER OF DETAILS IN BLUE PRINT 

DRAWINGS. 

Two Elevation of the Same Class in a Blue Print Drawing. . 56 

Three Detail Blue Print Drawing 58 

Two " " " " 63 

One " " " " 67 

Half " " " " 71 

PART V 

ANGLE PROJECTIONS 

Distinction Between Views, Elevations and Plans 54 

PART VI 

CROSS SECTIONS 

Angle Projection Elevation 74 

Cross Hatchings 76 

Cross Sections 78 

Center Line Cross Section 79 

Oft* Center Line Cross Section 82 

Quarter Cross Section 84 

Extended Out Cross Section 85 

Inserted Cross Section 86 

Broken Out Cross Section 87 

Zig Zag Cross Section 90 

Rib Cross Section 98 

Created Line Cross Section 100 

Complicated Cross Section 102 

Drawings 105 



CONTENTS 

PART VII 

ASSEMBLIES 

PAGE 

Assembly Blue Print Drawing 105 

Enlarged Assembly Blue Print Drawing .• 112 

Assembly Cross Sections 114 

Half Assembly Blue Print Drawings 132 

PART VIII 

MISCELLANEOUS IN BLUE PRINT DRAWINGS 

Details in Group Blue Print Drawings 134 

Separate Detail Blue Print Drawings 137 

Diagram Blue Print Drawing 138 

Gear Blue Print Drawings 139 

Spur Gear Blue Print Drawing 140 

Spiral Gear Blue Print Drawing 142 

Bevel Gear Blue Print Drawing 143 

Worm Gear Blue Print Drawing 146 

Movement of Travel in Blue Print Drawings 147 

PART IX 

CONVENTIONS 

Conventions 148 

Material Marks 148 

Scales 149 

Marks 150 

Gearing Marks 151 

Pattern Numbers 151 

Cross Hatchings 151 

Lines 154 

Center Lines 154 

Direction Arrows 155 

Dimensions 155 

Dimension Changes 156 

Title Blocks 157 

Bill of Materials 158 

Special Section Detail 158 

Positions 159 

Breaks 160 

Nut Proj ections 161 

Screws, Heads and Threads 162 

Tapped Holes 163 

Cored Holes 164 

Grouped Holes 164 

Bearings v 165 

Effects of Shading 166 

How a Blue Print Is Made 167 

Conclusion 169 



INTRODUCTION 

Realizing the need of a book of this nature, the 
author has endeavored to place before mechanics and 
others who are in need of instruction on the reading of 
blue print drawings, a book that contains a clear and 
comprehensive discussion in most simple terms. 

Throughout this book, I have used simple objects 
as illustrations upon which to base the instructions. 

Knowing that the weakness of many a writer of 
educational texts, lies in his failure to make known the 
things that are known to him as very simple, though 
in reality very hard to the reader, I have tried to men- 
tion such simple facts in my explanation as would 
prove to be a stumbling block if not understood by 
the student. I have endeavored to make the subjects 
interesting and appealing, so as to leave no doubt in 
the reader's mind of every step that would lead to a 
complete grasp of reading a blue print drawing. 

I do not wish to convey the idea that by studying 
this book, that the student can read a blue print draw- 
ing with the ease of a man who has given earnest study 
with long practical experience. I have not tried to 
teach the most complicated of blue print drawings, but 
to give the student fundamental principles, which with 
earnest efforts he may apply in practice. 

I am gratefully indebted to Mr. G. J. Lux of the 
Studebaker Corporation of this city for valuable sug- 
gestions and criticisms extended me for guidance while 
working on this manuscript. 

EDWARD R. VIGNEAU. 

Detroit Michigan, January 25, 1919. 

5 



KEY TO READING. 

In order that the reader may follow the subject 
more readily, the following type styles have been 
adopted throughout the book: 

Bold face type is used for emphasis, and in refer- 
ing to the chapter subject. 

Name of the object referred to, begins with Capital 
letter. 

CHAPTER TITLES, AND WORDS TAKEN FROM 
THE BLUE PRINT DRAWINGS, ARE SET ALL IN 
CAPITAL LETTERS. 






PARTI 



PERSPECTIVE DRAWINGS 



To begin with, look at Fig. 1 , which is a perspective 
view drawing of a box. 

A perspective view of an article is a representation 
of the article as it appears actually to our eyes. Many 
parts of the article thus appear in a single representa- 
tion. The perspective drawing in this respect differs 
from the blue print drawing or the working drawing, 
which shows each part in separate detail. 

Figure 1 , then, is not a working drawing, but a 
perspective drawing, as the foregoing explanation 
makes clear. 

In Fig. 1 the perspective 
drawing shows the ends and the 
sides of the Box is cut out in 
various shapes. The perspec- 
tive drawing pictures the Box 
as it might perhaps appear in 
reality. 

As you look at the Box as 

represented in Fig. 1 , you see 

three full views that form the 

right side, the front end, and 

top views, but you cannot see any of the bottom, or 

all of the left side and back end. The right side and 

the front end views are partly in front of them. 

In Fig. 2, which is the same Box as Fig. 1, three 
dotted lines have been placed. 




Fig. 1 



HOW TO READ 



DOTTED LINES 

Dotted lines, it may be said just here, are used in 
a blue print drawing to represent hidden lines. The 
dotted lines in Fig. 2, in part, outlines the bottom of 
the Box, as it would look in Fig. 1 if you could see 
through the right side and front end. 

In Fig. 2 the line from "A" to "C" can be only 
partly seen, because it is partly drawn full and partly 
dotted, which shows that the line from "A" to "B" 
can be seen above the side portion of the Box, but that 
the rest of the line which is from "B" to "C" cannot be 
seen, although it is understood as seen. Therefore, 

hidden lines to be understood 
as seen must be dotted lines. 
The last sentence is one of the 
general principles in blue print 
drawings. 

All dotted lines on a blue 
->rint drawing have something in 
front of them. When reading a 
blue print drawing, see what 
these dotted lines form. These 
dotted lines represent what lies 
back of the outside of the object drawn. 

To read understandingly the chapters that follow in 
this book, it is necessary for you to know exactly what 
dotted lines mean in a blue print drawing, for the mean- 
ing of dotted lines is one of the most important things 
to know for an understanding of blue print drawings. 

FULL LINES 

Full lines of any view drawing on a blue print draw- 
ing will always show you the outside shape and form 
for that view. 

Full lines seen in any blue print drawing reoresent 
parts openly seen without any surfaces standing in front 
of them. 

Figures 1 and 2 show the use of full and dotted 
(hidden) lines. 




Fig. 2 



BLUE PRINT DRAWINGS 9 

PLANE 

The term "plane" that is to be understood in the 
reading of blue print drawings is no less important than 
that of dotted lines. 

Let imagine a perfectly flat surface of glass, in 
thickness even thinner than a sheet of paper, is for 
all practical purposes to be considered a plane. In 
Fig. 3, let us think of the sheet, 1-2-3-4 as such a sur- 
face. 



VIEWS 

When a blue print drawing is made of any article, 
each side of the article as top, bottom, side or end is 
usually made into a separate view drawing, and the 
several view drawings are grouped around each other 
on a plane, so as to make a complete blue print draw- 
ing of the whole article. 

Each separate view drawing shown on a plane is 
commonly called a "view." By looking at each view, 
and studying each view at one time, a complete under- 
standing may be had of each and every part that can 
be seen in certain sides of the article that the blue print 
drawing may show. 

It is necessary that not only each side of the article 
represented be drawn on one plane as views, but that 
each view be grouped around one common view in 
such a manner that the relative positions of each side 
of the article drawn may be known as its view from 
the other views shown in a blue print drawing. 



10 HOW TO READ 



PART II 

STRAIGHT VIEW PROJECTION 

The word "projection" as applied to views, means 
that several sides or surfaces of an object are repre- 
sented point for point on a straight surface known as a 
plane. 

There are straight and angle view projections, both 
of which must be understood in the reading of blue 
print drawings. The straight view projection is that 
which is projected upon a plane in a straight to the 
edge of the drawing position. The angle view projec- 
tion will not be discussed at this time, because it will 
be much more readily understood after the straight 
view projection has been studied. 

In Fig. 3, you have represented the same Box as 
shown in Fig. 2 with the side 5-6-7-8 of the Box to lie 
in the plane 1-2-3-4. This plane is to be thought of 
as a transparent sheet of paper through which may be 
seen each move that the sides of the Box make as 
they swing into view upon the plane 1-2-3-4. This 
plane as has been stated, is in an upright slanted posi- 
tion. See Fig. 3. 

The side 5-6-7-8 of the Box of Fig. 1 is placed 
against the plane 1-2-3-4 of Fig. 3 with the Box itself 
projecting to the rear of the plane, leaving only the 
side 5-6-7-8 of the Box to be actually seen on the plane 
as illustrated in Fig. 3. 

Figure 3 shows only one view, for the other sides 
of the Box are not to be thought of as seen in the blue 
print drawing plane, unless these sides are swung 
around just enough to lie in the plane. It is only when 
the sides have thus been swung around, giving them 
position in the plane, that they become known as views. 
For convenience of illustration, hinges are to be 
imagined fastened to the Box as shown in Fig. 3. 



BLUE PRINT DRAWINGS 



11 



More than one view of the Box may be obtained 
as illustrated in Fig. 4. 

All sides of the Box of Fig. 4 may be imagined as 
swung on the hinges until the five sides lie against the 
plane 1-2-3-4 and are seen as five views. Particular 
stress must be given to your study at this point. 




Imagine that you see each side of the Box of Fig. 
4, swing into the plane from the original position as 
shown in Fig. 3. 

A very important point to be borne always in 
mind when reading a blue print drawing in straight 



12 HOW TO READ 



view projection is that the views are kept in the same 
relative position as the part of the object that they rep- 
resent. Note in Fig. 4, that the sides of the Box that 
are hinged to the side 5-6-7-8 are swung into the plane 
from the position occupied in Fig. 3, are the same sides 
of the Box as hinged to the side 5-6-7-8 that is in the 
plane 1-2-3-4 of Fig. 4. 

The sides of the Box which swing into the plane and 
become views should always be thought of when read- 
ing a blue print drawing as swinging into the plane in 
the direction of the opening hinges. Each view pro- 
jection that swings into position as another view to a 
plane, is that which existed between the several sides 
in their original position in Fig. 3. 

With the sides of the Box all hinged to the plane 
1-2-3-4, as shown in Fig. 4, so that all of the five sides 
lie in the plane, each view drawing is then called a 
straight view projection from the view that it is next to. 
When this is done, all sides of the Box are shown as 
views on a plane. 

The complete layout of views as seen in Fig. 4 is 
made to show the relation of each side of the Box to 
the other sides. Each side is a separate view only 
when the sides of the object drawn are shown on the 
plane. 

The above explanation may seem so simple to you 
that you may question the wisdom of giving so much 
attention to the way in which the sides of the Box are 
swung to the plane 1-2-3-4 as so many views to be 
studied in the drawing. It may be said that the Box 
was selected as a highly simplified example to which 
to apply these principles that will aid you later in 
understanding the projection of objects much harder to 
understand. 

Consider, for example, the Ratchet blue print draw- 
ing of Figs. 48 and 50, and you will realize the import- 
ance of the "hinge method" as an aid to understand- 
ing the way in which the end view is projected from the 
side view, 



BLUE PRINT DRAWINGS 



13 



In order that you may become skillful in reading 
with clear understanding the relation between views in 
a blue print drawing, you must carefully master the 
explanation given with regard to Fig. 4 so as to 
imagine the hinges as strapped to the sides of the Box 




for each view's position may then be more easily 
thought of in relation to the principle view, and in 
relation to the object itself. 

In Fig. 4, the sides are swung into the plane on 
hinges that keeps the views closely butted together. 



14 



HOW TO READ 



The relation between the views is clearly understood 
under these conditions. It is true, of course, that so 
far as relative position is concerned, the relation of the 
views, one to another is not changed, but only made 
clearer when the views are separated as in Fig. 5. You 




may further satisfy yourself as to the truth of this state- 
ment, if you consider that the sides of the Box are 
swung up to the plane 1-2-3-4, in Fig. 4 in such a way 
that all the sides are butted together, making each side 
with the side that is next to it look as if all of the sides 



BLUE PRINT DRAWINGS 15 

are in one view. Imagine that to change this crowd- 
ing together, you remove all of the hinge pins from 
the hinges and separate each view of the Boxes shown 
in Fig. 5. 

Having each view of the Box separated as in Fig. 5, 
the Box itself is shown by means of dashed lines in the 
position that is imagined to occupy when any one of 
the views is considered. Therefore, by means of 
dashed lines, the Box is shown in exact relation to each 
one of the views as it is considered. 

The complete Box as represented in the several 
positions in Fig. 5 as extending in back of each view 
on the plane, will aid the student in understanding 
the relation of one side of the Box as a view on the 
plane to any other side of the Box as a view on the 
plane. 

In Fig. 6, the Box is shown as in Fig. 5, only that 
the hinges are removed. 

As each of these views on the plane, as in Fig. 6, 
is shown with a complete outline of the Box extended 
back of the plane, each view shows by the use of dotted 
(hidden) lines all that is back of the surface of the 
view. This requires the use of imaginary projection 
lines such as shown in Fig. 6. These projection lines 
are only imaginary. They project from points which 
lie straight back of each view as is shown drawn on 
the plane. 

Occasionally, so called mechanics are seen, who in 
order to project the side of an object into a view on a 
plane, swing their hands in the direction that the 
imaginary hinge swings. While this practice is excus- 
able in one who has had little experience at the reading 
of blue print drawings, to one who really knows how 
to read a blue print drawing, it conveys an impression 
of inability to cope with the principle of projection so 
easily mastered. 

The projection lines shown in Fig. 6 will be more 
fully explained under the subject of "PROJECTION 
OF LINES AND POINTS." Before reaching that sub- 



16 



HOW TO READ 



ject, it will be well to note in Fig. 6 that the lines and 
points that each view shows, are projected or brought 
up to the plane. 

What has been explained regarding the use of 
full and dotted (hidden) lines applies in the same way 
to projection lines. 




In Fig. 6, the views that are openly seen are pro- 
jected on the plane in full lines. The parts of the ob- 
ject in back of the plane hidden actually by surfaces 
nearer the plane are projected on the plane in dotted 
lines. 






BLUE PRINT DRAWINGS 17 

The dotted (hidden) lines on the plane in the bot- 
tom view of Fig. 6 represent lines which are not openly 
seen. They represent hidden lines showing the thick- 
ness of the sides of the Box, and may be thought of 
as occupying a place in back of the plane straight oppo- 
site the bottom view. The bottom of the Box is thus 
nearer the plane and hides the top of the Box from 
actual sight. 

Of course, in the top view in Fig. 6, the position of 
the Box back of the plane is reversed. The top of the 
Box in this instance conceals the outside bottom. 

The thickness of the sides of the Box in Fig. 6, it 
will be observed, cannot be openly seen, except in the 
top view, it is therefore shown in all the other views 
with dotted (hidden) lines. The student should of his 
own accord find the relation of hidden and open sur- 
faces in each of the other views in Fig. 6, and note the 
use of full and dotted lines. 

Figure 6 offers opportunity for an extended study 
of line projections. The student should take ample 
time to master the principles illustrated in this figure, 
especially as they apply to projection lines, as well as 
the use of full and dotted lines. 

In Fig. 7 is shown the plane 1-2-3-4 with the sides 
of a Box projected as Views on a Plane. The method 
of obtaining these views has been explained in connec- 
tion with Figs. 3-4-5 and 6. 

It was with the purpose of securing the full mean- 
ing of blue print drawings that the foregoing illustra- 
tions of a complete Box extending back of each view 
with dashed lines was shown. The representation of 
the Box extending back of the plane in the various 
views, were intended to give the student a clear under- 
standing of the relation between the whole Box and 
each of the views, and of the relation of each view to 
each other view. 

All of the views shown in Fig. 7 were drawn ex- 
actly as were those shown in Fig. 4, and were separated 
as were those shown in Figs. 5 and 6. The view draw- 



18 



HOW TO READ 



ings in Fig. 7 are simpler than those in either Figs. 5 
and 6, because in Fig. 7, the views are shown without 
any other lines to confuse you. 

In all other blue print drawings, each view shown 
is to be thought of in relation to all other views exactly 




Fiff. 7 



as has been explained in connection with Figs. 3-4-5 
and 6 that illustrates the views and projections of the 
Box. 

The skillful blue print reader must learn to see in 
the blue print drawing more than is actually set down 
in lines. The views in Fig. 7, for example, should sug- 



BLUE PRINT DRAWINGS 19 

gest to the reader the various relations shown by dotted 
lines in Figs. 5 and 6. Figure 7 with its several simple 
views should give as clear ideas of the Box and its 
parts as do the views and projections in Figs. 5 and 6. 
When the student begins to feel that this is so, he may 
then rest assured that he understands the fundamental 
principles of straight view projection. An understand- 




Fig. 8 



ing of the above principles is the basis of mastery in 
the reading of blue print drawings. 

In Fig. 8 the plane is shown lying straight, but in 
all other respects bears the same to the plane as in Fig. 
7. Figure 8 shows every detail of a complete Box as 
it should be drawn, and as a blue print drawing should 
represent it under the conditions that have already 
been stated. 



20 



HOW TO READ 



In Fig. 9 is illustrated a method of projecting lines 
from one view to another view, which should be of con- 
siderable help in finding where one line or point of 
one view can be located on another view, should these 
imagined projection lines be followed from view to 
view. The above method can be applied to the read- 
ing of any blue print drawing. 





















5'fl KB 

SjSiSI Eippp 




HS? 
















■mUHUHUmE 






■ 






^^K^^SH^H 







Fig. 9 

There is a figure on each corner of the Box of Hg. 
9. By following the figures that are alike, you can 
match the corners that are the same. 

It would be well to re-read and follow the explana- 
tions given with the various cuts and figures given so 
far until you are very confident that you thoroughly 
understand the development from the perspective 
drawing of the Box in Fig. 1 , to the complete blue print 
drawing of the Box shown in Fig. 8. 

To test your understanding of the principles so far 
explained, you should read step by step only what the 
illustrations show in Figs. 1 to 8 and explain these illus- 
trations in your own words. 






BLUE PRINT DRAWINGS 21 



ANOTHER METHOD OF STRAIGHT VIEW 
PROJECTION 

Another method of obtaining straight view projec- 
tions may be illustrated with the drawing of the Claw 
Hammer, commonly called the Carpenter s Hammer, 
which is a tool that every man has seen and handled. 

In Fig. 1 is shown a perspective view of a Claw 
Hammer, in other words, a picture of a Claw Hammer 
as your eye generally sees it. A perspective drawing 
of Fig. 1 convevs no particular information as to the 
construction of the Claw Hammer. 

You will note from letter "A" in the perspective 
drawing of Fig. 10, that the hole which holds the 
Handle suggests very little detail as to the hole's shape. 
From what is seen at the end of the Claw Hammer in 
Fig. 1 0. it is not known whether the hole is straight or 
tapered, or how wide this hole is. The proper shaoe 
of the Handle hole can only be had from what the 
separate views show in the blue print drawing of 
Fig. 11. 

When a Hammer is represented, as in Fig. 1 1 blue 
print drawing, the dimensions and shape can be pro- 
vided for each particular part. A perspective drawing, 
like that of Fig. 1 could not conveniently show dimen- 
sions. 

The blue print drawing of Fig. 1 1 shows the cor- 
rect shape for each oart that is seen in a s'de of the 
Hammer as a view, besides the placing of dimensions 
can be arranged wherever needed. Of course, every 
blue print drawing of any other article provides like- 
wise. 

To understand clearly the method of obtaining the 
views shown in Fig. 1 1 , is to imagine that the lines 
drawn about the perspective drawing of the Claw 
Hammer in Fig. 10, is to represent the corners of a 



22 HOW TO READ 



glass box, and that your Hammer fits snugly into this 
box. 

The corners of this glass box are numbered 1-2-3- 
4-5-6-7 and 8 for convenience in referring to each side 
as a view of the Hammer, as it is necessary to refer to 
these sides separately in making a clear explanation. 

Since the Hammer fits snugly into this box of Fig. 
1 0, you look into one, and only one of the sides of the 
box, the walls of this box should prevent your seeing 
any other side of the Hammer, except that seen straight 
in back of the side that you look through. Only one 
side of the Hammer is then clearly in view. Suppose, 
for example, that you look through the 2-4-6-8 side 
of the glass box, paying no attention to the other sides 
for the present. This would give you the side view 
shown in Fig. 1 1 . 

The side view of Fig. 1 1 gives only those details 
of shape as belongs strictly to the side of the Hammer 
seen through the side 2-4-6-8 of the box. 

In the left hand end view of Fig. 1 1 , there are 
shown principally the width and height. The length, 
along with the curving shape and general outline can be 
seen only in the side, top or bottom views. The posi- 
tion of the eyes in looking at the L-H. end view of Fig. 
1 1 is like the position of the eyes in looking through 
the L-H. end view 1-2-7-8 of the box of Fig. 10. 

The right hand end view of Fig. 1 1 is like the posi- 
tion of the eyes when looking at the R-H. end view 
through the side 3-4-5-6 of the box in Fig. 1 0. 

When looking at any view shown in Fig. 1 1 , think 
of the eyes in a position as illustrated in Fig. 1 0, by 
looking through a particular side of the box that shows 
the side of the Hammer represented in the particular 
view. 

It is expected of you to look into the side 1-2-3-4 
of the box in Fig. 1 while getting an understanding 
of the top view, and into the side 5-6-7-8 of the box to 
eret an understanding of the bottom view as shown in 
the blue print drawing of the Hammer in Fig. 1 I. 



BLUE PRINT DRAWINGS 



23 



To understand more of the Hammer, as to how 
the Handle fits into the Hammer, is to look at the 
dotted (hidden) lines in the center of the side view 
of Fig. 1 1, shows not only the Handle fitting into the 
Hammer, but also the length and height of the hole 
into which the Handle fits. To see how wide the Ham- 
mer Handle hole is, you must look at either of the end 
views, or the top or bottom views of Fig. 1 1 . 

A part of the Handle can be seen in the top view, 
hence this part is shown with full lines. What cannot 



L-H 
CND 

view 




Fig. 10 

be seen of the Handle in the top view, are the parts 
hidden by the top of the Hammer above it, as is drawn 
with dotted (hidden) lines. 

In the bottom view of Fig. 11, all of the Handle 
that is not in the Hammer Handle hole can be seen, 
because when looking at the bottom of the Hammer, 
the claw on the top of the Hammer is not in the way 
of a full open view. 



24 HOW TO READ 



In the top view of Fig. 1 1 , the dotted lines show 
that the top of the Hammer has a receding curve which 
spreads across and is wider than the points that are 
below this top surface. The lower portion of the Ham- 
mer is thus covered from actual sight, though the blue 
print drawing reveals all lines that can be projected 
into the plane on the view in question. 

The small dotted line circle in the top view of Fig. 
1 1 represents the shape shown for the "N ,, - 4, 0" diam- 
eter part of the Hammer given as a short straight line 
in the side view. 

The projection (broken) lines that are seen from 
the small dotted line circle in the top view of Fig. 1 1 
are projected through to the side view until the points 
"N'V'O" are reached, which makes the points 
"N'V'O" i n the side view, the very same points 
' n '-"o" as seen in the top view. 

The points "n"~"o" as seen in the top view are ex- 
actly on the center line 15 and 20, and are the very 
same points "N"-"0" as those seen in the side view. 
The center line 1 5 and 20 of the top view is all of the 
plane that the side view occupied, because the side 
view is projected from the center line 15 and 20, to 
the side view plane. 

The hitting surface of the bottom part of the Ham- 
mer in the bottom view of Fig. 1 1 is shown in a full 
line circle, because when looking at the Hammer at its 
bottom or underside, there is nothing to obstruct a full 
open view. On the other hand, only a portion of the 
hitting surface of the Hammer is seen in the top view. 
This portion of the hitting surface is drawn in full line 
small curves "L"-"K,'\"F"-"H" and 'TVT'- These 
short full line curves in the top view r represent the por- 
tion not covered by the top part of the Hammer. 



BLUE PRINT DRAWINGS 



25 



The other letters in the different views of Fig. 1 1 
show where the points as placed by these letters in one 
view are to be found in another related view. You 
will note that the lines in one view are just the reverse 
in another view, with either dotted or full lines, as the 
case may be. 

If you do not understand fully the explanations 
just given of the projection of views of the Claw Ham- 





ffipis9^H 


■gfiB 

■US 


i^BH 


■MB ll| 

SNI 




ima 




Sgg 



Fig. 11 

»Tier, you should secure a Claw Hammer like the one 
in Fig. 1 0, and by looking squarely at each side of the 
Hammer, study it from the standpoint of the view 
drawings of Fig. 11 of that part. 

By comparing the detail, the parts as seen in the 
side as a view of the Hammer, each view shown in the 
blue print drawing of Fig. 1 1 will be easily under- 
stood. 



26 



HOW TO READ 



THE THIRD METHOD OF STRAIGHT VIEW 

PROJECTION 

In Fig. 1 2 is shown a perspective view of a Machin- 
ist's "V" Block which is represented by the drawings 
of Figs. 1 3 and 1 4 illustrating another way to project 
the sides of an object as views on a plane. 




Having the plane 9-10-11-12 as shown in Fig. 13 
which is lying flat and square to the plane 1-2-3-4, and 
the "V" Block as shown in Fig. 12 placed on the end 
of the plane 9-10-1 1-12, one can represent by the use 



BLUE PRINT DRAWINGS 



27 



of projection lines each surface of the "V" Block as a 
view projected upon the plane 1-2-3-4. 

In Fig. 1 3 is shown how the ends of the "V" Block 
are projected with projection lines to the plane for each 




Fig. 14 

of the end views. The R-H end view is shown by the 
course that the arrow "A" takes from the object to 
the plane, while the arrow "B" shows the course that 
the L-H end view takes to the plane. 

To understand how the top, the bottom and the 
side views of the "V" Block are projected to the plane 
1-2-3-4, the student should follow the course of the 



28 



HOW TO READ 



projection lines in the direction of the arrows "C'% 
"D**- , 'E" direct from the object to the plane as shown 
in Fig. 14. 

What is projected to the slanted plane 1-2-3-4 of 
the "V" Block in Figs. 1 3 and 14, is also projected to 
the upright plane 1-2-3-4. This upright plane 1-2-3-4 
is the natural position in which to show every plane. 
From now on, in the explanation of how to read blue 
print drawings, the plane will be shown in this natural 
position. 


















Fig. 15 



The plane separated from the slanted representa- 
tion of Fig. 1 4 is shown in its natural position in 

Fig. 15. 

In Fig. 1 5, it will be clearly seen after a little study 
that all of the views are not needed to convey full in- 
formation concerning the shape of the "V" Block, for 
each of the end views gives the same outline shape, and 
the same lines, hidden or open, may be shown in either 
the top view or the bottom view. 

Either the top view or the bottom view, and either 
one of the end views are the only views needed to 
work a combination with the side view for a complete 
representation of the "V" Block blue print drawing. 



BLUE PRINT DRAWINGS 



29 



Blue print drawings as previously explained, are a 
group of one or more views drawn to show the shape 
of one or more sides of an object represented by lines 
projected upon a plane. 

So far, for the convenience of explanation, we have 
shown every side of the object projected upon the 




- 



Fig. 16 Fig. 17 

plane, as in Figs. 8, 1 1 and 15, but every side of the 
object does not need to be shown in the blue print 
drawing, for in most cases, only three views are neces- 
sary. The three views most generally shown are the 
side, end and top views. 

In Figs. 16, 17, 18 and 1 9 are shown four separate 
blue print drawings of the "V" Block of Fig. 1 2. Each 




Fig. 18 



Fiff. 19 



blue print drawing is correctly drawn. Any one of the 
blue print drawings is all that is needed for a complete 
blue print drawing of the "V" Block. 

Fig. 1 6 shows the side and the L-H end view with 
a top view. Figure 1 7 shows the side and the R-H end 
view with a top view. Figure 18 shows the side and 
the L-H. end view with a bottom view. While Fig. 1 9 
shows the side and a R-H. end view with a bottom 



30 



HOW TO READ 






view. Each one of the above groups is drawn cor- 
rectly, and any one could be used as a complete blue 
print drawing of the "V" Block of Fig. 12. 

It is the practice of draftsmen to show in their 
drawings, views drawn with the least amount of dotted 

lines that is possible to 

show. You are not to infer 

from this that there should 

not be any dotted lines in 

any of the views, for the use 

of dotted lines depends upon 

what the views are to show. 

The top views of Figs. 1 6 

and 1 7 have no dotted lines, 

because there are no shapes 

below the top view to be shown in dotted (hidden) 

lines. The bottom view is undesirable, because that 

would have to be drawn with dotted lines. 

Therefore, the views in either Fig. 1 6 or Fig. 1 7 
would be the choice of a draftsman, although either of 
Figs. 1 8 and 1 9 might be drawn and be correctly 
understood. 

As has been explained with reference to Figs. 1 6, 
17, 18 and 1 9, that much depends upon the way a 
draftsman desires to arrange the views in a blue print 
drawing. He may use any 
one of the several arrange- 
ments to suit his purpose, 
yet there may be special 
advantages in a particular 
arrangement. 

A top view is always 
shown in preference to a 
bottom view, unless the Fig. 21 

bottom view is of such construction that it can not be 
shown drawn in the top view without too much com- 
plication of details, and only then is a bottom view 
generally used to avoid such undesirable complications. 
What has been said regarding a choice between a 
top view or a bottom view, applies also to a choice be- 




BLUE PRINT DRAWINGS 



31 




Fig. 22 



tween the two end views. Either one or the other of 
the end views is chosen, thereby avoiding the confusion 
that might easily arise through the use of too many 

views of the same class. 
As already stated, prac- 
tically only three views 
are necessary for a blue 
print drawing of any ar- 
ticle. It is well to note 
how Fig. 20 shows the 
projection of views for 
Fig. 1 7, likewise how the 
projection of Fig. 19 is 
to be thought of as illus- 
trated in Fig. 2 1 . 
The proper way to project a view from another 
view is illustrated in Fig. 22, and not like Fig. 23 
illustrates, which is the wrong way. Because of the 
danger of using this wrong method, much stress was 
given to the explanation of hinging of the Box in 
Figs, 3, 4, 5, 6 and 7. 

It quite often happens 
that persons not thorough- 
ly versed in the reading 
of blue print drawings 
undertake to project a 
L-H. end view upon the 
position of a R-H. end 
view as illustrated in Fig. 
23. 

It will be noted that 
the R-H. end view of Fig. 
22 would be like its L-H. 
end view, because the object happens to be of simple 
construction with both ends alike. But, for example, 
consider the confusion that would result were there 
an attempt made to exchange the position of the end 
view of the Ratchet in the blue print drawings of 
Fig. 50. 




Fiff. 23 



32 



HOW TO READ 



PROJECTING TO A PLANE WHAT LIES BACK OF 

THE PLANE 

Views projected upon a plane as explained so far 
must be thoroughly understood, that not only that part 

of the object in Fig. 24 
that is lying actually in the 
plane that forms the view, 
but also the parts that lie 
back of the plane, must be 
projected upon the plane. 
These parts must be 
brought up to the plane 
from the dash lines that 
form the perspective ob- 
ject drawing of Fig. 24. 
Upon the plane 1-2-3-4 



Fig. 24 

of Fig. 24 is shown only 
the edge of the base of the 
Bracket that lies in the 
plane, but this edge does 
not form a complete side 
view of the object. Every- 
thing extending back of 
the plane 1-2-3-4, must 
be brought up to the 
plane, so as to make the 
object a complete side 
view like that projected 
to the plane 1-2-3-4 in Fig. 25. 

What is projected on the plane 1-2-3-4 of Fig. 25 
in full lines represents the outside shape of the object. 
Lines that cannot be actually seen on the plane 1 -2-3-4, 
are the lines that are drawn dotted, because dotted 





Fig. 25 



BLUE PRINT DRAWINGS 



33 



lines in any kind of a view show hidden lines that can- 
not actually be seen. 

Figure 26 illustrates a hinging motion to obtain 
views, as explained of the Box. 

You will note from what has been said, that all 
full lines in a blue print drawing do not necessarily 
belong originally on the plane, because what is in back 
of the plane to be projected (brought up to) upon the 
plane, and represented in full lines, if it is in clear open 



Figure 26 shows the three planes, 1-2-3-4, 7-5-2-1 
and 2-5-6-3, which are no longer three planes as in 
Figs. 24 and 25, but opened out as one plane. These 




planes are shown separated in Fig. 27, and grouped 
about each other in the blue print drawing of Fig. 28 
in the same relative position as shown in Figs. 26 
and 27. 

By studying carefully the arrow lines in Fig. 28, 
and tracing the views from figure to figure, in Figs. 24 
to 28, a clear understanding will be arrived at re- 
garding the original position of the object represented, 



34 



HOW TO READ 



and the relative position of the views and methods of 
showing these views in the blue print drawings. 

7 





Fiff. 28 



BLUE PRINT DRAWINGS 



35 



PROJECTING OF LINES AND POINTS 

Figure 30 is a complete blue print drawing of a 
Sliding Jaw of a Machinist's Vise, which are shown in 
four views. However, only three views, which can be 
the side and top, with either one of the end views, is 
all that is needed to give a complete blue print 
drawing. 




Fig. 30 



The purpose in showing both the right and left 
hand end views of Fig. 30, is to show you why the face 
of the Jaw "A" as seen projected in the left hand end 
view from the side view cannot be seen in open view. 
For this reason, the face of the Jaw "A" is shown with 
dotted (hidden) lines, because the projection is upon 



36 HOW TO READ 

the side view in the direction of eye position No. 1 as 
shown in Fig. 29, while the same Jaw "A," shown as 
"B" in the R-H. end view of Fig. 30 can be seen, be- 
cause the Jaw "B" is open to full view in the R-H. end 
view, as it was projected from the side view in the 
direction of eye position No. 2, as imagined in the per- 
spective drawing of Fig. 29. 

In Fig. 3 1 is shown a perspective view of a Jaw 
Body of a Machinist's Vise which no doubt you are 
familiar with. There is good training in examining 
the actual perspective objects of Figs. 29 and 31 
as are represented by blue print drawings, as the student 
learns thereby to picture objects in his mind's eye as he 
looks at the blue print drawing. 

In Fig. 32 is shown a complete detail blue print 
drawing of the Jaw Body of the Vise as drawn in three 
views, as three views give all the details needed to 
show the entire construction of the Jaw Body part of 
the Vise. 

By following the dashed arrow lines in Fig. 32 
from one view of the object to its other views, and con- 
tinuing the same dashed arrow lines to its perspective 
view of Fig. 3 1 you can readily appreciate how one 
line in a view, if projected to another view can be more 
fully understood. Each and every view of any blue 
print drawing contains the very same lines or points, 
but seen in their different view positions, and giving 
some additional source of information for each view. 

When reading a blue print drawing, the reader 
should at all times train his mind upon all of the views, 
so that when projecting one or more lines from one 
view to that of another view, get in mind a picture, 
such as the perspective view of Fig. 3 1 shows for Fig. 
32. Then such lines as make up the Jaw Body part 
shown in the blue print drawing of Fig. 32, will be as 
clearly seen and understood as the perspective Jaw 
Body view of the Vise in Fig. 3 1 . 

An understanding of the projecting of lines and 



BLUE PRINT DRAWINGS 



37 



points is of great importance in the reading of blue print 
drawings. 

The method explained in this chapter is practically 
the same in many respects as the method of projecting 
views to a plane, but instead of projecting a view to a 




Fig. 32 



plane, a line or point is projected from a part of one 
view to the views that are next to it. 

The principle projection lines and points are shown 
extending from one view to another view in Fig. 32. 



38 



HOW TO READ 



Figure 33 shows a Stand correctly represented in 
every respect in the blue print drawing in Fig. 34. 

The lines connecting each view of Fig. 34 are pro- 
jecting lines which are used, as has been explained, in 
tracing the position of lines or points from one view to 
another view. 

Any particular line or point in a view of any blue 
print drawing that does not readily show the location of 

the line or point in its 
next view, must be looked 
for in the next view along 
a parallel to the edge pro- 
jection line to that view, 
as shown in Fig. 34. 

In every blue print 
drawing, there is one view 
that suggests practically 
the main idea of the ob- 
ject drawn. Since this one 
view of a group of views offers so much, that view 
must be sought for the main source of information. 

For example, consider the half round circles "W" 
and "X" of the side view of Fig. 34, which side view 
is the main view for understanding the whole blue 
print drawing, so far as the half round circles "W" 
and "X" are concerned in the various views of Fig. 34. 
To locate the half round circles "W" and "X" in the 
end view, look straight across the line * 4 A"-' 4 B." 
..£,. ♦•£)•• anc j "P". 44 F" from the points 'W-^C'-^E" 
of the side view, and as the points <, A"-"C"-"E" of 
the side view are seen only on one side of the end view, 
then the half round circles "W"-*'X" as seen in the 
side view are only to be on one side of the end view, 
which is the left hand side of the R-H. end view. 




Fig. 33 



BLUE PRINT DRAWINGS 



39 



To confirm that the half round circles "W" and 
"X" as seen in the side view of Fig. 34 is shown only 
on one side of the end view, look at the top view of 
Fig. 34 along the straight upright projection lines as 
you did in tracing the half round circle points "W" and 
"X" in the end view. 

As the points "A ,, -"C"-"E" of the side view are 
the only points that the upright projection lines of the 
half round circles "W" and "X" show on one side of 




Fig. 34 



the top view, it is known, therefore, that the half round 
circle openings "W" and "X" as shown of the side 
view of Fig. 34, are only on one side of the object, 
as represented in Fig. 33. 

The two half round circles "W" and "X" as seen 
in the side view are each openly seen located in their 
respective positions in the top view of Fig. 34, because 
they are there in full open view, but the half round cir- 
cle "W" and "X" are not both seen together in the 



40 



HOW TO READ 



end view as they are in the top view, because the half 
round circle "X" is first seen with dotted (hidden) 
lines in the end view, and the half round circle 4 'W" is 
to be thought of as being straight in back of, and in 
line, and as far apart with the half round circle "X" as 
shown on the side view. 

The lines showing the half round circle "X" pro- 
jected from the side view of Fig. 34, to the end view, 
are also the same lines that show where the half round 
circle "W" is seen in the end view. The half round 




Fig. 35 



circle "W" must be straight in back of the end view of 
the same distance apart as in the side view of Fig. 34 
show. 

The projection lines as shown in the blue print 
drawing of Fig. 34 to connect each view, are for the 
purpose of aiding the eyes to follow the lines to the 
same point on the other views. 

Draftsmen should not draw these projection lines 
as in Fig. 34 on any kind of a blue print drawing, be- 



BLUE PRINT DRAWINGS 



41 



cause the projecting lines would become confused with 
the lines of the drawing. The reader of a blue print 
drawing should imagine that he sees these projection 
lines. Draftsmen who draw such lines thereby show 
their inexperience. 

Since blue print drawings should have no projec- 
tion lines to connect the views as in Figs. 35 and 36, 





Fig. 36 



it is a good practice for the beginner to use a straight 
edge or rule parallel to the edges of the blue print 
drawing as shown in Figs. 35 and 36. 

It is well to note in Figs. 35 and 36 that each rule 
or straight edge serves as a guide in tracing a line or 
point of one view to the very same positions in the 
other views. 



42 



HOW TO READ 



Figure 37 shows a perspective draw- 
ing of the Ratchet disc as shown in the 
blue print drawing of Fig. 38. 



The projection lines that connect the 
side with the end views of Fig. 38, show 
how the dotted as well as the full lines are used in rep- 
resenting the teeth in the end view. The lines of the 
outside edge of the teeth are shown with full lines in 




Fig. 38 



the end view, because the outside edge is open to full 
view, while the dotted lines in the end view show the 
lower edges of the teeth, which are hidden by the upper 
edges, when projected from the side view. 



BLUE PRINT DRAWINGS 43 




Practice Reading Figure 



44 



HOW TO READ 



Figure 40 shows a complete blue print drawing of 
the four hole Block of Fig. 39. 

In the top view of the blue print drawing of Fig. 
40, are shown four holes lettered "A," "B," "C" and 
"D". These holes as shown in the top view of Fig. 
40, must also be located in the side and end views, as 
shown with dotted (hidden) lines as in Fig. 39. 




Fig. 40 



The dotted (hidden) lines in the side view of Fig. 
40, represent what is seen in the side view of the per- 
spective drawing of Fig. 39. The dotted (hidden) 
lines for the sides of the holes "A" and *B" are in- 



BLUE PRINT DRAWINGS 45 



termingled in the side view as projected from the top 
view of Fig. 40. 

The holes "C" and "D" of the right hand side of 
the top view of Fig. 40 are projected to its side view. 
One side of each of the holes "C" and "D" of the side 
view intermingle and show only the line t4 M"~"N," be- 
cause each hole as seen in the top view is offset from 
the other just far enough, so that the intermingling of 
the dotted line "M"-"N" in the side view seems to be 
only one line, although it really represents two lines, 
this is because the dotted line "M"-"N" of the side 
view represents the side of the holes "C" and "D" that 
are in line with each other. 

In the end view of Fig. 40 are dotted lines to rep- 
resent four holes, but from first glance at the end view, 
only two holes seem to show. 

The last paragraph should be borne in mind when 
looking at any view of any blue print drawing, that it 
is necessary to look at more than one view before de- 
ciding upon all facts concerning the object repre- 
sented. 

In the left hand side of the R-H. end view of Fig. 
40, is seen the hole "C" projection, but straight in back 
of, and in line with the hole "C," is the hole "B," as is 
seen in the top view, which hole "B" is understood to 
be back of the hole "G," as both the holes "C" and 
"B" are apart in the end and top views. 

The hole "D" is also first seen in the right hand 
side of the R-H. end view of Fig. 40, but the hole "A" 
is straight in back of and in line with the hole "D." 

The above paragraphs will be readily understood 
by the student if he carefully examines Fig. 39 in rela- 
tion to Fig. 40. 



46 



HOW TO READ 



EXAMPLES OF VIEW PROJECTIONS 

Figure 4 1 shows a perspective view of the Bracket 
Slide represented by the blue print drawing of Fig. 42. 

Each view of Fig. 42 is encased with a dashed 
arrow line pointing to the perspective view of Fig. 4 1 , 
of where each view is obtained from the object, and 




MQ 



iitii^. 



Fig. 42 



the relative position that each view in Fig. 42 has to 
each other view. 

The four views as shown in Fig. 42 are more views 
than are needed. Either one of the end views of Fig. 
42 is all that is necessary with the top and side views. 



BLUE PRINT DRAWINGS 47 

A complete blue print drawing of the object repre- 
sented in Fig. 4 1 requires only a top, side and end 
view. Each of the end views of Fig. 42 conveys the 
same information, hence the use of either one of the 
end views will do to make a complete blue print draw- 
ing. The R-H end view will be used, as R-H end 
views are generally used in blue print drawings. 

The R-H end view of Fig. 42 shows the Slide 
drawn in dotted (hidden) lines, because the Slide is 
not openly seen, as the Lug is in front of it. In the L-H 
end view, the Slide can be openly seen, hence the Slide 
is drawn in full lines, as that view has the Lug to the 



The encased dashed arrow lines around each end 
view of Fig. 42, and pointing to its side of Fig. 41, 
should give a good understanding why the Lug was 
drawn dotted in one end view and not in another. 



48 



HOW TO READ 




Figure 43 shows a perspec- 
tive view of an Arm Bracket 
which is fully represented in the 
blue print drawing of Fig. 44. 



Fig. 43 




Fig. 44 



BLUE PRINT DRAWINGS 



49 




Figure 45 shows a per- 
spective view of a Lever 
Latch which is also fully 
represented in the blue 
print drawing of Fig. 46. 



Fig. 45 




Fig. 46 



The views shown in Figs. 41 to 46 should be used 
in reviewing the principles governing the projection of 
views, lines and points. 



50 



HOW TO READ 



INFORMATION THAT ONE VIEW OFFERS 
ANOTHER 



In Fig. 48 is show a blue print drawing of a Ratchet 
Wheel. The perspective drawing of Fig. 47 shows 
what the blue print drawing of Fig. 48 represents. 

The blue print drawing of Fig. 48, has a side, a 
R-H end and a top view, which is enough information 
of the Ratchet shown in Fig. 47. 

Figure 48 could also show a L-H 
end view, but such a L-H. end view 
is not needed, as it would not add 
any additional information, for the 
side, end and top views as shown in 
the blue print drawing of Fig. 48, 
contain every detail that could be 
shown in a L-H. end view. 

The object of this lesson on the 
Ratchet of Fig. 47, is to point out 
the importance of each view in rela- 
tion to its other views of a blue print 
Fig. 47 drawing. 

To begin with, it is seen in the side view of Fig. 48, 
that the hexigon shape is seen drawn with dotted lines. 
As dotted lines always show what is hidden, then the 
hexigon as drawn in the side view must represent the 
back part of the Ratchet for that view. In the top and 
end views of Fig. 48, this hexigon shape can be seen 
openly. 

Should the "hinging method" of projecting views 
to a plane as explained of the Box be applied to Fig. 
48, it would show clearly and simply the side of each 
view on which the hexigon shape is found. 

Truly, the blue print drawing of Fig. 48 is drawn 
in a simple manner so as to be clearly understood, as 
all blue print drawings should be. Blue print drawings 
are often seen, however, as shown in Fig. 50, which 




BLUE PRINT DRAWINGS 



51 



can be easily understood by one who thoroughly knows 
how to apply the fundamental principles, but at best, 
the blue print drawing of Fig. 50 would be puzzling 
and a stumbling block to most mechanics. 

The cross sectioned end view of Fig. 50 has not the 
advantages of the views in Fig. 48, because in Fig. 50 
there is not the hexigon and dotted tapered hole as 
that shown in the top and R-H. end views of Fig. 48 to 
guide you. 





I 

1 1 






1 ■■(] ■ 


' ■Si /"" 


1 1 


^EHO 




'. i 
■ fi | I 

B"B| 






IB 






Isl 


^H 


;iaTll?l»l ■!'"• ^H 



Fig. 48 

It was intended by the draftsman to give no other 
consideration to an understanding of the cross sec- 
tioned end view as shown of the hexigon, other than 
that shown in the side view of Fig. 50, for the drafts- 
man took it for granted, that those who were to use the 
blue print drawing of Fig. 50, would know how to 
read it. 



52 



HOW TO READ 





Fig. 49 



The cross sectioned end view as shown in Fig. 50, 
is at this time out of the regular order of our explana- 
tion, as the subject of cross sections will be more fully 
explained under Part VI on "CROSS SECTIONS" to 

follow later. 

Such blue print 
drawings as that shown 
in Fig. 50 reveal the 
real use of the "hinging 
of views" to a plane, 
that every one should 
know well enough to 
apply. 

When looking at 
the end view of Fig. 50, 
the side of the Ratchet 
that the hexigon shape 
is on, may be easily 
found if the end view is projected from the side view 
to the plane in the same manner as explained of the 
Box. 

To find which side of the end view of Fig. 50 that 
the hexigon shape is on, is to note that the hexigon 
shape in the side view is dotted, which means that 
the hexigon shape is hidden from full view, and that 
there must be something in front of it. Well then, 
the circle "A" of Fig. 50 is drawn with full lines, 
hence circle "A" must be in full open view, and on 
the front side of the side view. If circle "A" is in 
front, then the hexigon must be back of the side view. 
By projecting the views to a plane, as explained of the 
Box, it is an easy matter to find on what side of the 
end view of Fig. 50 that the hexigon shape is. 

To strengthen the explanations given thus far on 
this subject, observe that the circle "A" which is seen 
in open view in the side view of Fig. 50 goes thru 
the point "B" where the hidden point of the hexigon 
meets the center line 44 ]"_ 4 '2" of the side view, mak- 
ing with the circle "A," at the point *'B," one com- 
mon point. When this "B" point is projected across 



BLUE PRINT DRAWINGS 



53 



to the end view of Fig. 50, the straight line "b"-"b" 
is formed. Likewise the common point "C" when 
projected, forms the straight line "c"-"c," showing 
that the diameter for the round side of the Ratchet's 
end in the side view is the same as the extreme diameter 
of the points of the hexigon on the center line "1 "-"2." 
A mechanic who does not throughly know, after 
a little study, the meaning of such an end view as 
shown in Fig. 50, is not thoroughly versed in the prin- 
ciples of projecting a view to a plane, which he should 




Fig. 50 

above all things know thoroughly. Such an end View 
of Fig. 50 may ordinarily be of a more puzzling nature, 
as the comments "ROUND END" and "HEXIGON 
END" were only given on Fig. 50 to help aid in the 
explanation. 

A good rule always to remember when seeking to 
get from one view, information of another view, is that 
in projecting a view to a plane, that the nearest side of 
the next view to the one you are considering, is the 
same side of the view that you are considering. 

What has been explained of the Ratchet and its 
views of Fig. 50, applies in like manner to any other 
views in any other blue print drawing. 



54 



HOW TO READ 



PART III 

THE DISTINCTION BETWEEN VIEWS AND 
ELEVATIONS OR PLANS 



The word "view" is used in naming the sides of 
an article when projected to a plane in a blue print 
drawing, as was used so far in these explanations. 

The word "view" is not in the strict sense the 
proper word to use, although it is in general use among 
those who read blue print drawings. 

The word "view" actually means what is seen of 
an object from any position that is within scope of the 
eye, which would apply more correctly to the perspec- 
tive views as given in Figs. 1, 10, 12, etc. Therefore, 




Fig. 51 

such sides of an article as are projected to a plane 
should not in the proper sense be called "views," as 
that word conveys a hazy meaning. Instead of the 
word "view," use the word "elevation" or "plan." 

The word "elevation" in blue print drawings is 
used when speaking of the side of an object represented 
in an elevated or upright position, as a fence, or the 
side of a building, etc., showing no vanishing points, 
as that of a perspective view. 

The word "plan" must not be confused with the 
word "plane," for a plan is the representation of an 



BLUE PRINT DRAWINGS 



55 



article seen on a flat surface, such as the position a 
building occupies of the ground as may be seen from 
an airplane. 

A good illustration of a plan is given in Fig. 5 1 , 
showing the arraignment of the fixtures and the shape 
of a bath room floor. Another good example is seen 
in Fig. 52 showing the layout in the form of a map. 
The map is a good example of a plan. 

In our explanations from now on, the side of any 
article as projected to a plane, which was previously 




Fig. 52 

called a view, is to be called an elevation or a plan. 
The following statements make clear the meaning of 
the words that will be used: 

A side view is a side elevation. 

A R-H. end view is a R-H. end elevation. 

A L-H end view is a L-H end elevation likewise. 

A top view is a top plan, and 

A bottom view is a bottom plan. 



56 HOW TO READ 

PART IV 
TWO ELEVATIONS OF THE SAME CLASS IN A 
BLUE PRINT DRAWING 

A back, elevation in a blue print drawing is a rare 
thing, for a back elevation is most generally combined 
into the front elevation by the use of dotted (hidden) 
lines. Should a back elevation be too complicated to 
give the proper details when drawn with dotted lines 
into the front elevation, then a back elevation is made 
into the drawing with a notation placed below, stating 
that it is such an elevation. 

The blue print drawings of Fig. 55 is made up 
with sections "A" and "B," for the purpose of show- 
ing two elevations of the same class in a blue print 
drawing, instead of only one elevation of the same 
class as is usually done. 

In showing the two side elevations, as the front and 
back (side) elevations of Fig. 55, the need of the two 
elevations of the same class for a blue print drawing 
is illustrated. In some blue print drawings there is 
too much detail to show in only one side elevation with- 
out an extra amount of dotted (hidden) lines that 
would be confusing. This is true of the blue print 
drawing in Fig. 55, which represents not only the 
front and back parts of the Slide Bracket, but also the 
slot "S" at the center. 

The blue print drawing of section "A" of Fig. 55, 
is sufficient to show all that would ordinarily be re- 
quired for Figs. 53 and 54. 

In the blue print drawing of the Slide Bracket, in 
which there is the slot "S" at the center to be shown, 
as well as the front and back parts, two separate ele- 
vations of the same class are shown to make clear what 
the dotted lines represent of the slots. 

The only reason for ever showing two side eleva- 
tions as in the section "B" of the blue print drawing of 
Fig. 55, is to show the front (side) elevation in full 



BLUE PRINT DRAWINGS 



57 



lines (is open to full view), and the back (side) eleva- 
tion in full lines (also open to full view) , and to secure 
the difference of between lines not transposed from full 




to dotted or from dotted to full lines when viewed 
separately in each of the side elevations. 

You will note in the front and back (side) eleva- 
tions of section "B" of the blue print drawing of Fig. 
55, that the lines forming the construction of the slot 




58 HOWTOREAD 

"S" were not transposed from dotted to full lines, 
showing that those dotted (hidden) lines form the in- 
side construction of the slot "S." The dotted lines of 
the slot *'S" would mix up with those of the back con- 
struction in a confusing way ,if the front (side) eleva- 
tion alone were shown as in section "A" of Fig. 55. 
The slot "S" as shown in the front (side) elevattion 
can be seen, of course, in the top plan. 

THREE DETAIL BLUE PRINT DRAWINGS 

The three detail 
blue print drawing 

as shown in Fig. 
5 7 with two ele- 
vations and a top 
Fig. 56 plan, is the kind 

most generally 
used. Such a blue print drawing gives three sources of 
information. 

The word "detail" as used in connection with blue 
print drawings means simply the portion of the blue 
print drawing that an elevation or plan shows, like the 
top, the side or end elevation when considered sepa- 
rately from the whole blue print drawing. Each sepa- 
rate elevation or plan is known as a detail. 

Almost any number of details may be shown in a 
blue print drawing, all depending upon the nature of 
the article drawn, which generally ranges from one, to 
as high as six details, and sometimes even more in 
an ordinary blue print drawing. 

A three detail blue print drawing is generally what 
every blue print drawing shows, so as to give enough 
detail of what is seen in each side of the article drawn. 

Figure 5 7 offers two elevations and a top plan for 
a blue print drawing, which is all that is needed to give 
the necessary information for the perspective drawing 
of Fig. 56. 



BLUE PRINT DRAWINGS 



59 



A L-H. end elevation added to Fig. 5 7 would only 
show the Lug in a position opposite to that in which 
it is shown in the R-H. end elevation. Furthermore, 
such L-H. end elevation would necessarily have to be 
on the other side of the side elevation, where every 
L-H. end elevation belongs, and such would add no 
extra detail, other than what is shown in the R-H. end 




Fig. 57 



elevation of the blue print drawing. Therefore, a 
draftsman would not use his valuable time in making 
an extra detail, which would be useless. 

A bottom plan placed also in the blue print draw- 
ing of Fig. 5 7, with what is now shown, would not add 
any additional detail for a better understanding, other 
than what the top plan now shows. The only differ- 
erence in having a bottom plan shown, is that in pro- 
jecting the bottom plan to the plane, there would be 
shown dotted (hidden) lines that are now seen in the 
top plan in full lines. Likewise, what is now seen in 
the top plan in dotted lines would be shown in a bot- 
tom plan in full lines, with the exception of the circle 
opening, which would be the same in the bottom plan, 
as now seen in the top plan. 



60 



HOW TO READ 



Figure 59 is a blue print drawing of Fig. 58, which 
also has two elevations and a top plan. The details 
shown give sufficient information of the construction of 
Fig. 58, without any other additional elevations or 
plans. 

It will be timely to dwell at this time on Fig. 59, 
and to review what was learned of the hinging of the 
Box as treated and explained in straight view projec- 
tion. Apply the "hinging method" of obtaining the 
R-H end elevation to the plane from the side eleva- 
tion of Fig. 59. What is your understanding of the 
instructions you have received so far of straight view 




projections? What end of the side elevation of Fig. 59 
is it that projects in back of the R-H end elevation? 
The answer is, that the end as shown in the plane 
5-6-7-8 of Fig. 58 is the end of the side elevation that 
lies in back of the R-H end elevation, and that the end 
of Fig. 58 that lies in the plane 1-2-3-4, is the end that 
shows in the R-H end elevation of Fig. 59. 

From the last paragraph can be seen the real mean- 
ing of the planes 1-2-3-4 and 5-6-7-8 of Fig. 58. This 
should be a very good reminder of how the R-H end 
elevation was projected to plane from the side eleva- 
tion of Fig. 59. 



BLUE PRINT DRAWINGS 



61 



Should there be a L-H end elevation of Fig. 59 
blue print drawing, what is seen through the plane 
5-6-7-8 of Fig. 58 would be what is seen first in the 
L-H end elevation, and all that lies straight in back of 
the plane 5-6-7-8 would then be projected up to the 
plane of Fig. 59 to form a complete L-H end ele- 
vation. 

If a L-H end elevation were shown in the blue 
print drawing of Fig. 59, everything that is seen of the 




Fig. 59 



R-H end elevation as shown would be the same for 
the L-H end elevation, with the exception of line num- 
ber 9. Line number 9 would be drawn dotted in the 
L-H end elevation, instead of being drawn full as in 
the R-H end elevation. This is because the Lug which 
is in front of the bottom surface cannot be actually 
seen in a L-H end elevation, but only imagined as 
seen. 



62 



HOW TO READ 



The lines of the blue print drawing of Fig. 59 as 
shown with the number 1 0, should help you to find 
where those lines as shown in one elevation or plan 
can be seen where they belong in each one of the other 

elevations or plans. 

Figure 61 is a blue print 
drawing which has two ele- 
vations and a top plan to be 
used in the making of the 
object shown in the perspec- 
tive drawing of Fig. 60. 

You will note that the ar- 
rangement of each elevation 
and plan of Fig. 61 is out 
of the regular order for details, which makes it differ- 
ent from those shown so far, with the exception of 
what has been explained of Figs. 16, 17, 18 and 19. 





Fig. 61 



BLUE PRINT DRAWINGS 



63 



The arrangement of the elevations and plan of the 
blue print drawing of Fig. 61 is correct in every re- 
spect, but if desired, the end elevation could be shown 
as a top plan, or a side elevation. Likewise, the top 
plan could be shown where the end elevation is now 
located. The end elevation would then be placed 
where the top plan is now placed. Such an arrange- 
ment is hardly ever made, because a top plan placed 
differently, would not be shown as the top of the 
article in its natural position. Should the elevations 
and the plan of Fig. 61 be so located, then the eleva- 
tions and the plan would become different elevations 
and a different plan by the position they occupy in the 
whole blue print drawing. 

i 
TWO DETAIL BLUE PRINT DRAWINGS 



ANCLE SLOT 




Fig. 62 



Figure 63 is a blue 
print drawing contain- 
ing a top plan and a 
R-H end elevation 
which is all the infor- 
mation that is needed 
to show the construc- 
tion of the object in 
the perspective draw- 
ing of Fig. 62. 
The top plan alone of the blue print drawing of 
Fig. 63 would not convey the necessary information 
concerning the object of Fig. 62 without some other 
elevation to work with it. A R-H end elevation there- 
fore is provided, although a L-H end elevation or a 
side elevation could be placed with the top plan in- 
stead of the R-H end elevation as shown, and just as 
much information can be obtained from such an ar- 
rangement. 

To show a bottom plan, instead of the top plan, 
as in Fig. 63, would require reversing what is now 
shown in the top plan, that is, the angled full lines 



64 



HOW TO READ 




Fig. 63 

of the top plan of Fig. 63 would have to be drawn 
dotted, and the dotted lines as shown in the top plan 
would have to be drawn with full lines in a bottom 
plan. Besides the turning around of the R-H end ele- 
vation relation to a converted bottom plan, if it was 
arranged that way. 

A side elevation of the 
blue print drawing of Fig. 63 
is not needed, because such 
information can be had by 
looking at the top or bottom 
side of the R-H end eleva- 
tion, from which can be im- 
agined a side elevation of 
Fig. 63. 

Hie angled slot as shown 
in the top plan can be seen 
in the R-H end elevation for 
its depth, because in the 
R-H end elevation, the 
dotted line "A" shows how 
deep the slot is from the out- 
side surface. The dotted line of the end elevation of 
Fig. 63 is suggested in Fig. 62 with a dotted line. 

In Fig. 65 is represented with two details for a 
blue print drawing of an Off Set Yoke Bell Crank as 
shown in Fig. 64. 




Fig. 64 



BLUEPRINT DRAWINGS 



65 



The blue print drawing of Fig. 65 is not complete 
in every detail concerning the Yoke Bell Crank. The 
shape of the corners is not shown in the blue print 




Fig. 65 

drawing of Fig. 65. Of course Fig. 64 shows that they 
are round, but Fig. 64 is not drawn on a blue print 
drawing, and Fig. 65 does not show that the corners 
are round or square. 




Fiff. 66 

With a three detail blue print drawing, there would 
have been no question of understanding for lack of 
detail. 

A top plan like Fig. 66, given a place on Fig. 65 
blue print drawing would convey all the necessary in- 



66 



HOW TO READ 



formation for the corners in question, but this would 
be the only need of such a top plan in Fig. 65. 

Should the side elevation of Fig. 65 be drawn with 
shaded lines, as Fig. 6 7 shows, only a two detail blue 
print drawing like Fig. 65 is all that would be needed. 
Figure 66 as a top plan in Fig. 65 would not then be 

needed, for the 
shaded lines in 
Fig. 67 would 
show the round- 
ness of the cor- 
ners. Since the 
amount of the 
roundness of the 
corners would 
have to be guessed 
at, the top plan of 
Fig. 66 in its place 
with Fig. 65 could 
be used to good 
advantage. 

Such shading lines as has been dwelt on in the 
above paragraphs will be more fully treated on in the 
subject of "CONVENTIONS." 




Fig. 67 




Figure 69 represents with two details, a blue print 
drawing of the Off Set Lever Arm shown in Fig. 68. 

With the top plan and side elevation that make up 
the blue print drawing of Fig. 69, there is not shown an 
end elevation, because an end elevation can be im- 



BLUE PRINT DRAWINGS 



67 




Fig. 69 

agined from what is seen of the top plan and the side 
elevation. The addition of an end elevation to Fig. 
69 would not help in any way. 

ONE DETAIL BLUE PRINT DRAWINGS 

One detail blue print drawings are not used very 
often, because they lack detail, and such one detail 
blue print drawings are limited to general application. 



c 



D 



Fig. 70 

Each of Figs. 70 to 78 could be drawn with end 
elevations, but such are not needed, for all necessary 
information is contained within these one detail blue 
print drawings. 



68 



HOW TO READ 



As the one detail blue print drawing, as shown and 
treated on at this time, is so closely connected with the 
subject of "CONVENTIONS" that will be treated later, 
we will now only lightly touch upon the subject of one 
detail blue print drawing. It is necessary to take the 
subject up now, as one detail blue print drawings are 
often used to show a complete blue print drawing. 




Fig. 71 

Figure 7 1 is a blue print drawing of a round Bar, 
as shown in Fig. 70. If this Bar is not too long, a round 
circle is cross hatched inside of same to show that it is 
round. Should a one detail blue print drawing of Fig. 




Fig. 72 

7 1 be shown without the round cross hatched circle, it 
would not be understood without an end elevation. 
The mechanic would not know whether it was intended 
to be round or square. 



a) 



Fig. 73 



A cross hatched circle as shown in Fig. 71 is called 
an Inserted cross hatching, which will be treated further 
in the subject of "CROSS SECTIONS." 



BLUE PRINT DRAWINGS 



69 



Should Fig. 7 1 be extra long, too long to be drawn 
on a blue print drawing, then a break is shown in the 
Bar, like that of Fig. 72, which by its shape would show 
that the Bar is round, hence no round cross hatched 
circle like that in Fig. 71 is needed to show that the 
Bar is round. 




Fig. 74 

Figure 74 is a torn out part of a blue print draw- 
ing of a Shaft, with keyways placed as shown in Fig. 
73. The top part of the Shaft of Fig. 74 is shown 
broken out, so that cross hatching may show a separa- 
tion of the metal that the Shaft is made of, from that 
of the position of the keyways. 




Fig. 75 



Figure 74 shows the regular way of representing 
keyways in Shafts. Keyways are used only on Shafts, 
and since all Shafts are round, no other lines are 
needed. If a blue print drawing is made to represent 
an object other than a round Bar, with a key way in it, 
then that object is a different shape and considered spe- 
cial, and for special instruction, which can be given in 
detail by means of another elevation or plan. 

Fig. 75 is a blue print drawing of the same con- 
struction as Fig. 74, but instead of showing the key- 
way within a broken out section, the keyways are drawn 
dotted, because the dotted lines shows that the con- 
struction is not open to full view. 




70 HOW TO READ 



Figure 76 is a Cotter Pin 
known to all machine trades- 
men. A drawing as in Fig. 76 
is all that is necessary, because 
Fig. 76 of the article's commonness. 

Its construction must not be of 
any other nature than along the manufacturers' stand- 
ard, otherwise, another elevation or plan would be 
necessary to show its special construction. 

Figure 77 shows a one detail blue print drawing of 
a Ball. The one detail is all that is necessary to repre- 
sent the Ball. The circle drawn without the shading, 
as Fig. 78 shows, would convey no meaning, unless a 
note were placed under same to give further informa- 
tion as to the meaning of the circle. 

An end elevation or a top plan of the Ball placed 
beside the side elevation of Fig. 78, would make a 




Fig. 77 Fig. 78 

group of circles, which circles would naturally be of 
the same size and would cause confusion. Therefore, 
if a Ball is to be drawn for a blue print drawing, shad- 
ing as in Fig. 77 must be made to show that it is a 
Ball. 

A mere circle to represent a blue print drawing of 
a Ball, as in Fig. 78, would not be understood, for such 
a circle could be thought of as a circle of a plate. 



BLUE PRINT DRAWINGS 



71 



HALF DETAIL BLUE PRINT DRAWINGS 

The purpose of making a 
half detail blue print drawing 

would not apply for all classes 
of objects, but only to such ob- 
jects as a Wheel, Pulley, etc., 
which are made up of two 
parts exactly alike. 

The purpose in drawing a 
half detail blue print drawing 
such as that shown in Fig. 80, 
is to save work by making only 
Fi 7g half of the drawing rather than 

the whole. 
Another reason why a half detail blue print draw- 
ing is used, is because a half detail may be drawn 
larger, so as to permit larger space for details which 
could not be shown in the cramped space of a smaller 
drawing. 

It must be understood that a half detail blue print 
drawing can only be made of an object whose two 
halves are exactly alike. 





Fig. 80 



To know that a blue print drawing is only a half 
detail, is to know that what is shown of the center line 
construction "A ,, -"B" of Fig. 80, and what lies on that 
center line must then be through the diameter. 



72 



HOW TO READ 




Fig. 81 

Figure 8 1 is a complete blue print drawing of Fig. 
79 that was shown drawn with a half detail blue print 
drawing in Fig. 80. 

In Figure 83 is shown a half detail blue print draw- 
ing similar to that explained in Figs. 80 and 81, the 
only difference being that Figs. 80 and 81 have six 
spokes, while Figs. 83 and 84 have only five spokes. 
Figure 84 is a complete blue print drawing of a 
five spoke Wheel which was 
shown drawn with a half detail 
blue print drawing in Fig. 83. 

It was said in the explana- 
tions for Fig. 80, that in order 
for a half detail blue print 
drawing to be drawn, the half 
that is drawn, must be like the 
half that is not drawn, but in 
Fig. 83, the half that is drawn, 
is not like the half that is not 
drawn, because it shows three 
spokes in the top half of Fig. 
83, while the bottom half would only have two spokes. 
This condition is taken care of with a note above the 
detail of Fig. 83, stating, "NOTE— 5 SPOKES 




Fig. 82 



BLUE PRINT DRAWINGS 



73 



EQUALLY SPACED," which note meets the objection 
of not showing each half, when the halves are unlike. 

Figure 84 is a complete blue print drawing of a five 
spoke Wheel that was shown drawn with a half detail 
blue print drawing in Fig. 83. 




Figr. 83 

The dimensioning of the diameter of the half detail 
blue print drawing can be understood in Fig. 80, for its 
diameter is shown, but most generally in such half de- 




Figr. 84 

tails, the diameter is shown like in the end elevation of 
Fig. 83, with the dimension line extending past the 
center line '*D"-"E" which is to be understood as the 
whole diameter. 



74 



HOW TO READ 



PART V 




Fig. 85 



ANGLE PROJECTION ELEVATION 

Almost every blue print 
drawing is of the straight pro- 
jection kind, but often a blue 
print drawing, like Fig. 87, has 
an angled projection. 

Figure 87 shows a complete 
angle projection blue print 
drawing, with all the details of 
elevations and plans that are 
necessary in representing the 
Arm Bracket shown in Fig. 85. 
The method of projecting the side elevation to the 
plane from the top plan, in Fig. 87, is somewhat dif- 
ferent from the general run of blue print drawings. 

First: — The side elevation as shown projected to 
the plane of Fig. 87 is where the end elevation is gen- 
erally located in almost all blue print drawings. This 
does not matter, as was explained before, because any 
projection can be made from any elevation or plan. 

Second: — The side elevation as projected to the 
plane from the top plan of Fig. 87 is shown drawn in 
an angled or slanted position is explained on the prin- 
ciple of the triangle shown in Fig. 86. 

In Fig. 86 is shown a right angle 
triangle. The undeniable law of 
the right angle triangle is: That 
the hypotenuse is opposite the 
right angle which is the longest 
side (or leg). Should the tri- 
angle not be a right angle triangle, 
then the side opposite the greater 
angle of the triangle is the longest 
side of the triangle. 

In the top plan of Fig. 87, you 
will find two triangles, one numbered "1-2-3" and the 
other "1-3-4," having the line "1-3" as the one corn- 




Fig. 86 



BLUE PRINT DRAWINGS 



75 



mon hypotenuse for both of the triangles. These two 
triangles are butted or placed together, making with 
the two triangles, the rectangle "1-2-3-4." 

The side elevation of Fig. 87 is projected to the 
plane from the top plan in an angled or slanted posi- 
tion, which in this case is the proper position for the 
side elevation to be projected from the top plan, as 
shown in the blue print drawing of Fig. 87. 




Fig. 87 



The side elevation of Fig. 88 is shown drawn with 
dashed lines, as the way almost all blue print drawings 
show their side elevation projected position. But the 
side elevation of Fig. 87 is not drawn on the same prin- 
ciple as the side elevation of Fig. 88. The side eleva- 
tion in Fig. 88 is not properly projected, because it is 
projected from the leg "3-4" of the triangle, which is 
shorter than the hypotenuse "1-3," which is not the 



76 HOW TO READ 



true length of the Arm of the Arm Bracket, where as 
the side elevation of Fig. 87 is projected from the top 
plan from the hypotenuse "1-3," which is the true 
length of the Arm of the Arm Bracket. 

The explanation in the last paragraph makes clear 
that the side elevation of Fig. 87 is correct, and that 
the side elevation as shown in Fig. 88 is not correct 
for a blue print drawing where there are elevations or 
plans projected from an angled object, such as the top 
plan of Fig. 87 shows. 

PART VI 
CROSS HATCHINGS 

Cross hatching is made of several slanted lines 
grouped into a design or symbol that has a general 
meaning to those who understand the reading of blue 
print drawings, as the symbols of Fig. 89 show. When 
any one of these symbols is drawn into a cross section, 
like that in Fig. 91, it represents the material to be 
used in making the articles drawn. 

Each cross section may show with one or more of 
the several styles of the slanted symbols, as in Fig. 89,. 
what is desired of what the blue print drawing show. 

Some draftsmen vary in degree on one or more of 
the several symbols of materials as shown in Fig. 89. 
Some may use a symbol to convey a different meaning 
than that is shown in Fig. 89, but these differences are 
generally done by those draftsmen who are more or 
less lacking in experience and practice. 

Figure 89 does not, however, show every symbol 
that may be used at times, for a symbol may be created 
by a draftsman to show some special materials. 

Should you not readily understand what a symbol 
of material means in a blue print drawing, you can 
always find out, for the name of the material is also 
generally shown below the elevation or plan of the 
detail, but such material is never stated in an assembly 
blue print drawing. 



BLUE PRINT DRAWINGS 



77 



When symbols of cross hatching of Fig. 89 are 
used in an assembly blue print drawing, it is to princi- 
pally show the separation pf one or more parts that 
compose the whole assembly, besides what the cross 
section is to show. 

There is no rule as to how far apart these slanted 
cross hatch lines should be, as in Fig. 89, but it is 




Cast Iron 



Cast Steel 



Wrought Copper, Brass 
Iron or Compositon 




Cast Steel Wrought Steel Aluminum 







Original-Fill 
Earth 



Sand 



Concrete 



Concrete 
Block 






Cross- Length- 
wise wise 
Wood 



Glass 



Water 



Fig. 89 



Brick 



Symbols of cross hatching. 

expected that the spacing of cross hatchings will be 
equally placed apart, according to the size of the space 
that the cross hatching occupies. 

The reader should memorize and know at sight, 



78 HOW TO READ 



the different symbols of material, so that when he sees 
a cross hatching in a cross section, he understands what 
the material is that is represented in the blue print 
drawing. 

CROSS SECTIONS 

This chapter on cross sections is of great impor- 
tance, for it enables the reader of a blue print drawing 
to understand many special facts not obtained other- 
wise. 

Should a blue print drawing that you are to read 
be made up by a capable draftsman, that draftsman 
will make use of cross sections quite freely, so as to 
make as far as possible his drawings self-explanatory. 
One who is versed in the fundamental principles of 
blue print drawings will know what is meant with but 
little study and effort. 

The main rule to follow in making a cross section 
of a blue print drawing, is to show what is to be 
imagined of the detail of the object, if it were cut 
into two parts, so as to show the shape of the section 
that is in view when the parts are separated. 

A cross section of any blue print drawing is the 
only place where a cross hatching (as explained in the 
last chapter) can be used, that is why a cross section 
is always known at a glance. The design or symbol 
of material that is to be used is at once noticeable. 

Cross sections are not shown in every kind of a 
blue print drawing, because many blue print drawings 
are simple in design and need no extra helps to the 
mechanic. Cross sections are most generally used in 
elevations and plans to show the shape of a corner or 
thickness. They are used especially when an elevation 
of a blue print drawing is complicated in shape. 

All cross sections of any blue print drawing are 
always taken from a line, which is most generally from 
the center line of the elevation or plan that is next to 
the elevation or plan in which the cross section is 
shown. In other cases, a cross section may be taken 



BLUE PRINT DRAWINGS 79 

from a created line to show where a cross section is 
desired. 

There are various classes of cross sections, which 
are: 

Center line cross sections 

Off center line cross sections 

Quarter cross sections 

Extended out cross sections 

Broken out cross sections 

Inserted cross sections 

Zig zag cross sections 

Rib cross sections 

Created line cross sections 

Assembly cross sections. 
Each of the above cross sections will be explained 
in the same order as here listed. 

CENTER LINE CROSS SECTION 

In Fig. 9 1 is a blue print drawing of a Wheel, the 
end elevation of which shows a center line cross sec- 
tion. This Wheel is shown by the use of the side and 
end elevations, which are all the elevations that are 
needed for a blue print drawing of the Wheel, because 
the addition of any other elevation or plan would add 
nothing to the meaning of the detail of the object to 
make it clearer, other than what the blue print drawing 
of Fig. 9 1 shows. 

The end elevation of the Wheel in Fig. 9 1 shows a 
cross section which was taken from the center line 
"A" — "B" of the side elevation. This end elevation 
cross section of Fig. 91, like all cross sections of any 
blue print drawing, is always looked for on the center 
line of the elevation that is next to the end elevation 
that is cross sectioned. 

The center line "A" — "B" which passes thru the 
side elevation of Fig. 91, and extends as the same 
center line * V — * "b" thru Fig. 90, is that which you see 
cross hatched in the end elevation of Fig. 9 1 . 



80 



HOW TO READ 



The half of Fig. 90 that is cross hatched, is to be 
imagined as that seen in the center line of the side 
elevation of Fig. 9 1 , and given in detail in the end 
elevation. 




Fig. 91 

To make the last paragraph apply as an explana- 
tion of all center line cross sections of every detail of 
any blue print drawing, train your mind to imagine 
that what is seen thru the center line of the side eleva- 
tion, if same were cut in half, would be that as shown 
in Fig. 90 cross sectioned end. 



BLUE PRINT DRAWINGS 



81 



What has been explained of Figs. 90 and 91, ap- 
plies exactly to Figs. 92 and 93, with the exception 
that the end elevation of Fig. 93 is not a cross section. 

si 




Fig. 93 



Figures 91 and 93 are drawn for the purpose of 
comparing an elevation that is cross sectioned with one 
that is not. 

In Fig. 93, the vertical center line "A" — "B" that 
passes thru the center of the side elevation, also passes 
thru the dotted section of the web of the Wheel in 



82 HOWTOREAD 



Fig. 92. This dotted section of the Wheel is the same 
as that projected by the use of dotted lines from the 
center line of the side elevation to the end elevation 
of Fig. 93. 

The dotted section as shown in the end elevation 
of Fig. 93 is that half of the side elevation of the 
Wheel that is shown by the arrows directed at each 
end of the center line of the Wheel of Fig. 93. 

It is seen from the above paragraph, that it is not 
necessary that an end elevation of any blue print draw- 
ing should be cross sectioned, only that cross sections 
assists and helps the reader of a blue print drawing to 
a better understanding, especially should the drawing 
be complicated in nature. 

In comparing Figs. 91 and 93, each figure is drawn 
correctly, and either one or the other of the Figs. 9 1 
and 93 could be drawn, as each may be used alone 
with but little difference as to the possibilities of it 
being understood. It is most likely that Fig. 9 1 would 
be the choice of a draftsman in drawing a Wheel. 

OFF CENTER LINE CROSS SECTION 

In explaining Figs. 90 to 93, it was stated that 
when any cross section is made on any elevation or 
plan of a blue print drawing, that it is generally found, 
and may be looked for on a center line of one of the 
elevations or plans that is connected with the cross 
section of the object drawn. 

Should you after seeing the cross section in the end 
elevation of Fig. 95 be unable to understand within a 
few moments by looking at the center line of the 
elevation that is next to the cross sectioned end eleva- 
tion, of where the cross section comes from, you are 
then to look for remarks below the elevation or plan 
that is cross sectioned. 

The remark "SECTION ON D— D" as stated be- 
low the cross sectioned end elevation of Fig. 95, 
should direct you to the line "D — D," and not to the 



BLUE PRINT DRAWINGS 



83 



center line of the side elevation where the cross section 
comes from. 

By extending the line "D — D" in the side elevation 
of Fig. 95 straight up thru Fig. 94, would change the 




Fig. 95 



off center line "D — D" of Fig. 95 to "d — d" of Fig. 
94 from which the end elevation of Fig. 95 is to be 
realized. 



84 



HOW TO READ 




Fig. 97 

QUARTER CROSS SECTION 
This problem of quarter cross section is somewhat 

the same in principle as the cross sections already 

explained. 

The quarter cross section, like the end elevation of 

Fig. 97, is drawn usually this way by draftsmen so as 



BLUE PRINT DRAWINGS 35 

to gain time, and at the same time convey just as full 
meaning of the center line as the other cross sections 
already explained. 

When a cross section like that shown over the 
horizontal center line "D-B-C" of the side elevation 
of Fig. 97 is not a complete cross section for the whole 
of the end elevation, then remarks as are shown below 
the end elevation of Fig. 97 are to be looked for, 
telling where in the side elevation that the cross section 
does come from. 

Below the end elevation of Fig. 97 are the words 
"SECTION ON A-B-C." The end elevation is to be 
projected from the line "A-B-C" of the side elevation, 
which would show exactly what the eye could see when 
looking straight from the center of the vision lines of 
the eye position number 1 of Fig. 96, when the "F" 
section of the Wheel is imagined as taken away. What 
is seen from the eye position number 2 is not to be 
seen in the end elevation, but imagined as seen. 

The cross section of the end elevation of Fig. 97 
is generally considered by one who reads blue print 
drawings that the shape cross hatched for the top half, 
is to be the same shape as the bottom half, which is 
not shown cross hatched. 

The shading as shown in the end elevation of Fig. 
97 is to represent the roundness of the face of the 
bottom half of the Wheel, which is not cross sectioned. 

EXTENDED OUT CROSS SECTION 

In Fig. 98 is shown a complete blue print drawing 
of a Lever Handle, with the perspective drawing of 
Fig. 1 00 to help in the following explanations. 

Extended out cross sections are cross sections 
shown extended out from an elevation or plan, with 
remarks stated below each, such as: — "SECTION ON 
A-B," and "SECTION ON C-D" as seen on the blue 
print drawing of Fig. 98, is what is projected from the 
lines "A-B" and "C-D" of the end elevation. 



86 



HOW TO READ 



The extended out cross sections as seen in the blue 
print drawing of Fig. 98, is seen for its position in the 
Lever as shown in Fig. 1 00. 

The extended our cross sections, as the/ 'SECTION 
ON A-B" of Fig. 98, answers practically all that a top 
plan could offer for information of the Lever, there- 




Fig. 100 



Fig. 98 



fore a top plan is not needed for Fig. 98, but were the 
"SECTION ON A-B" not shown, then a top plan 
would be needed to show the roundness at the part 
"A" of the end elevation. 



INSERTED CROSS SECTION 

An inserted cross section is a cross section for a 
particular part or section placed inside of an elevation 
or plan. 



BLUE PRINT DRAWINGS 



87 



The line "C-D" of the end elevation of Fig. 98 as 
seen extended out and cross sectioned is all that is 
needed to show a cross section of that particular part 
of the Lever, but should there not be an extended out 
cross section as shown, and should there be any cross 
section desired at that point of the lever, an inserted 
cross section could be shown inside of the side eleva- 
tion instead. 

When an inserted cross section, such as is shown 
upon line "C-D" in the side elevation of Fig. 98 is 
used, the extended out cross section "C-D" as ex- 
tended out from the end elevation is not needed, for 
they both show the same detail. 

BROKEN OUT CROSS SECTIONS 

In the end elevation of the blue print drawing of 
Fig. 98 are shown three broken out cross sections 
which are to represent the parts of the Lever shown 
by the encased arrow lines of Fig. 99. 

What is seen cross hatched in the broken out cross 
sections of the end elevation of Fig. 98, is to be under- 
stood as on the center lines of the side elevation, for, 
as was explained before, that all cross hatchings are 

most always shown on cen- 
ter lines, unless there are 
remarks given below the 
elevation of where the 
cross section did come 
from. 

The reason for show- 
ing broken out cross sec- 
tions in Fig. 98, is to give 
Flff - 101 a combination of the in- 

side, as well as a part of the outside of any elevation 
or plan. 

Figure 1 02 is a complete blue print drawing of the 
Flange Bearing shown in Fig. 101. 

The R-H end elevation of Fig. 1 02 shows an- 
other broken out cross section for the purpose of 
showing in open view, the outside of the hole "B," 




88 



HOW TO READ 



and the inside of the part "A" of the Flange Bearing, 
without using dotted lines as in the end elevation of 
Fig. 103. 

The broken out cross section of the R-H end ele- 
vation of Fig. 1 02 is not really necessary, for the R-H. 
end elevation of Fig. 1 03 could be shown instead. 




Figr. 102 

The L-H end elevation as shown on the side of the 
blue print drawing of Fig. 1 02 is not needed, because 
the R-H. end elevation shows the broken out cross 
section of the outside of the hole "B," while in the 




Figr. 103 



BLUE PRINT DRAWINGS 



89 



L-H end elevation of Fig. 1 02, what is shown in dotted 
lines of the hole "B" has a hazy meaning. 

Were all of the R-H end elevation of Fig. 1 02 to 
be cross hatched, it would be impossible to show the 
hole "B," from the direction of the center line ar- 
rows No. 3 of the side elevation direct, would not con- 
tain the hole "B," although the end elevation could 
be cross hatched to show the hole "B" if imagined pro- 
jected from the arrows No. 1 of the side elevations. 




Fiff. 104 

Should the broken out cross section be not shown in 
the R-H end elevation of Fig. 102, then a L-H end 
elevation, such as that shown in Fig. 1 04 could also 
in its proper place be used to give complete informa- 
tion of the end elevation. 

Figure 103 is a correct blue print drawing of the 
Flange Bearing of Fig. 101. The opening "A" as seen 
in Fig. 1 1 and shown with dotted lines in the end 
elevation of Fig. 1 03 is not as clearly understood as 
the same R-H end elevation of Fig. 1 02 would be with 
a broken out cross section. 

The position of the hole "B" in the L-H end eleva- 
tion of Fig. 1 04 is seen in its position, because the hole 
"B" as shown in the L-H end elevation is in the half 
of the side elevation of Fig. 1 04 marked by the ar- 
rows of the center line in the direction of No. 2. 



90 



HOW TO READ 



ZIG ZAG CROSS SECTIONS 

One of the chief advantages of the zig zag cross 
section in a blue print drawing is shown by the special 
Block of Fig. 1 06. 

In Fig. 1 06 is shown a complete detail blue print 
drawing of the Block represented in Fig. 105. 

d 




Fiff. 106 



BLUE PRINT DRAWINGS 



91 



Below the end elevation cross section of Fig. 1 06 
are the words: "SECTION ON A-B-C-D," which 
means that the cross section was taken from the line 
"A-B-C-D" of the side elevation. 
d 




Fig. 108 

What is shown cross sectioned. in the end eleva- 
tion of Fig. 1 06 is to be understood in the side eleva- 
tion as that which is shown cross hatched in Fig. 105. 



92 HOW TO READ 



The advantage of the zig zag cross section end ele- 
vation as taken from the line "A-B-C-D" of the side 
elevation of Fig. 106, is that it shows all the shape of 
the holes and openings of the side elevation in full 
open view in the end elevation, but should the end 
elevation of Fig. 1 06 be taken from the center line 
"D-E" instead of from the zig zag lines "A-B-C-D," 
then the end elevation of Fig. 1 06 would be like that 
shown of the end elevation of Fig. 1 08. 

In comparing Fig. 1 06 with that of Fig. 1 08, it 
will be found that both are drawn correct, but that the 
end elevation of the zig zag of Fig. 1 06 gives clearer 
detail of the "H" and "K" openings of the Block, 
than the end elevation of Fig. 1 08 does, because the 
end elevation of Fig. 1 06 is projected from the side 
elevation as that which is seen openly from "A" to 
"B," from "B" to "C" and from "C" to "D." In Fig. 
1 08, the cross sectioned end elevation is taken from 
the center line "d"- 4 V of the side elevation which is 
unlike the cross sectioned end elevation of Fig. 1 06, 
because in Fig. 108, the openings "h" and "k" are 
seen in the cross sectioned end elevation with dotted 
(hidden) lines as being back of the center line "d"- 
"e." The explanation for this is clearly shown for the 
relation of Fig. 1 05 to Fig. 1 06 and likewise in that 
of Fig. 107 is" to Fig. 108. 

In Fig. 1 1 is shown another example of the zig 
zag cross section in the blue print drawing of a Die 
Block. This Die Block is shown with three openings 
in its side elevation that could not appear on one com- 
mon center line, because a center line cross section 
could be used in showing the openings back of the 
center line only in dotted lines, which would not then 
be a zig zag cross section. To show these openings 
so as to get a clear open section for the end elevation 
of Fig. 1 1 0, it is necessary to take a cross section along 
the zig zag line "A.-B-C-D-E-F" of the side elevation. 

The end elevation of Fig. 1 1 is a zig zag cross 
section, which below this end elevation are the words: 



BLUE PRINT DRAWINGS 



93 



"SECTION ON A-B-OD-E-F" as projected from the 
side elevation. The end elevation should be imagined 
as all of the cross sectioned end of the Die Block "M" 
taken apart on the zig zag line "a-b-c-d-e-f" in 
Fig. 109. 




igi is 
=3 ^B E 



Fig. 110 

All of the cross hatched ends of the Die Block 
"M" of Fig. 109 are the very same as those cross 
hatched in the plane of the end elevation of Fig. 1 1 0. 
These are to be thought of as projected from the side 
elevation to that of the end elevation by the use of the 
imaginary horizontal projection lines that start at the 
opening as drawn in the side elevation through the end 
elevation. 



94 HOWTOREAD 



The lines named with capital letters that pass 
through the end elevation of t ig. 1 1 are shown in 
the end of the Die Block "M" of Fig. 109 with small 
letters, should enable you to compare them with those 
lettered with capital letters. 

In Fig. 1 09, the cross hatched end of the Die Block 
"M" is all that is seen in the end elevation of Fig. 
1 10. The side "N" of the Die Block is not to be 
thought of when looking for information in the end 
elevation. In order to see any of the "N" half of the 
Die Block, it is necessary to show another cross sec- 
tioned end elevation on the other side of the side ele- 
vation, which would have to be a L-H. end elevation, 
which is not needed in Fig. 1 1 0. The end elevation 
as drawn answers all that is necessary. Any other 
information that may be necessary can be gleaned 
from the side and end elevation of Fig. 110, is easily 
understood by referring to the separation of the Die 
Block of Fig. 1 09. 

In Fig. 1 1 3 is shown a blue print drawing of an 
Engine Cylinder. Figure 1 1 1 and 1 1 2 help show an- 
other example of a zig zag cross section blue print 
drawing. 

It will be noticed in Figs. 1 1 1 and 1 1 2 that only 
half of the Cylinder in picture-like form are needed in 
showing the elevations and plans of Fig. 1 1 3. 

The three plan cross sections shown in the top of 
the blue print drawing of Fig. 1 1 3 are to be imagined 
as taken from different positions noted along the zig" 
zag lines shown in the side and end elevations. 

All of the three plan cross sections shown in the 
top of the blue print drawing of Fig. 1 1 3 could have 
been placed anywhere on the blue print drawing of 
Fig. 1 1 3 as long as the notations as seen placed be- 



BLUE PRINT DRAWINGS 



95 



low these cross sections, were also placed below the 
same sections wherever they might have been placed 
on the blue print drawing of Fig. 1 1 3 so as to mark 
them in relation to the side and end elevations. 




Fig. 113 



The meaning of the line "M-N" in the ''SECTION 
ON M-N" shown in the side elevation of Fig. 1 1 3 is 
understood by examining the plan cross section shown 
in the center and at the top of the blue print drawing. 



96 HOW TO READ 



The encased broken arrow line which directs to the top 
of Fig. 1 1 2 gives an easier way of understanding the 
meaning of the line "M-N" of the side elevation of 
Fig. 113. 

The line "M-N" of the side elevation of Fig. 1 13 
is a straight line cross section, which is like almost all 
common cross sections. It is unlike the other two 
cross sections shown in the blue print drawing of 

Fig. 1 1 3. 

The plan cross section "E-F-G-H-J-K" as seen 
above the side elevation of the blue print drawing of 
Fig. 1 1 3 is not the same in principle as the cross sec- 
tion "M-N," because the cross section "M-N" was 
taken on a straight line, and the cross section "E-F-G- 
H-J-K" is taken from the zig zag line * 'E-F-G-H-J-K" 
of the side elevation of Fig. 113. By means of the 
broken arrow line pointing to Fig. 112, the zig zag 
cross section "E-F-G-H-J-K" may be easily under- 
stood. 

The zig zag plan cross section "E-F-G-H-J-K" as 
shown above the side elevation of the blue print draw- 
ing of Fig. 1 1 3 may also serve the purpose of showing 
the bridges "X" and "Y" from two separate planes 
to be on one plane, thus showing the necessary detail 
in one cross section without making another cross sec- 
tion. 

Should there be no note above the cross section 
plan "E-F-G-H-J-K" concerning the bridges "X" and 
"Y" stating that they were not on the zig zag plane, 
then the section "E-F-G-H-J-K" as shown above the 
side elevation of Fig. 1 1 3 would be understood as on 
the zig zag plane of the cross section plan. 

Without the note shown in the cross section plan 
"E-F-G-H-J-K" concerning the location of the bridges 
"X" and "Y," another cross section plan would be 
necessary. 



- 



BLUE PRINT DRAWINGS 97 



Should a straight line cross section be taken from 
the side elevation from "E" to "K" instead of from 
the zig zag line "E-F-G-H-J-K," what would be seen 
in the top plan cross section of the bridge "X" and 
"Y" would be drawn with dotted (hidden) lines. A 
zig zag cross section can therefore be more clearly 
understood, because it lays practically everything in 
one plane, open to full view. 

The section line "A-B-O-P" as shown in the L-H. 
end elevation can be used to show by the dimension 
arrows, how far apart these openings are. See Fig. 111. 

The cross section plan as placed above the end 
elevation cross section of the blue print drawing of 
Fig. 113, is taken from the zig zag line "A-B-C-D,*' 
which is given in Fig. 111. 

The object of the zig zag cross section "A-B-C-D," 
is to show the bridge "X" and the thread "T," which 
are on two planes of Fig. Ill, as if shown on one 
plane in the cross section plan above the end eleva- 
tion of Fig. 113, in full view of one cross section with- 
out the use of any dotted (hidden) lines. 



98 HOW TO READ 



RIB CROSS SECTION 

In Fig. 1 1 6 is shown a blue print drawing of a 
Bracket with two elevations and a top plan to its side 
elevation. 

As stated below the L-H end elevation, "SEC- 
TION ON C-D," is to be thought of as a cross section 
taken through the center line "C-D" of the top plan. 

The object of this problem is not for the purpose 
of showing how a cross section is to be understood 
in relation to its other elevations, for that has been 
previously explained, but for the purpose of making 
understood the particular cross hatching shown. 

In the L-H. end elevation of Fig. 1 1 6 is shown the 
main body of the Bracket detail with close-spaced line 
cross hatching. Its rib is spaced twice the distance of 
the spacing of the main body of the Bracket, or in 
other words, the rib cross hatched lines are every 
other line from the cross hatched lines of the main 
body of the Bracket detail. 

The object in cross hatching the rib every other 
line from the main body of the Bracket, is that a rib 
of any article that runs length ways may show by the 
cross hatching that it does belong to the main body 
proper, but as a solid connecting member only. 

The cross section of Fig. 1 1 4 shown by the dotted 
(hidden) lines "E-F-G" suggests the difference in 
thickness between the main body of the Bracket and 
that of the rib. 

Should a cross section be taken from the line "A- 
B" of the R-H end elevation of Fig. 116, the rib 
would be considered in the R-H. end elevation as a 
solid connecting member to the main body of the 



BLUE PRINT DRAWINGS 



99 



Bracket as it is a regular cross section, because it was 
cross sectioned crosswise. 

A rib of any main body, as shown in the L-H. end 
elevation of Fig. 1 1 6, would show cross hatching every 
other line apart from the main body, because it was 
cross sectioned lengthwise. 




Fig. 114 Fig. 115 

Care and study of the above mentioned rules 
should be a watchword in all blue print drawings that 
show ribs and thin surfaces. 




Fig. 116 

There is to quite an extent, a big practice among 
draftsmen not to cross hatch a rib or thin surface as 
explained with Fig. 1 1 4, and such unexperienced prac- 
tice of draftsmen should likewise be taken note of. 



100 



HOW TO READ 



CREATED LINE CROSS SECTIONS 

Figures 1 18 and 120 are each a separate and com- 
plete blue print drawing of Figs. 1 1 7 and 119 re- 
spectively. 

The R-H end elevation of Fig. 1 1 8 shows the posi- 






R5! 








SECTION ON G-H 


SECTION ON J-K 
J 


A E 


G 

1- 1 


- -----t 

SIDE ELEVATION 


K 


B 

R-HENDELEV. 


l HI 



Fiff. 118 

tion of the part "E" in relation to the center line "A- 
B," which end elevation is all that is needed to convey 
the meaning of the blue print drawing of Fig. 1 1 7. 

Should a cross section be desired in Fig. 1 1 8 from 
either of the created lines "G-H" or "J-K," such cross 
sections at these particular points could be placed any- 
where on the blue print drawing, so long as it is stated 
below these cross sections where they were taken from, 
however, with the R-H. end elevation as shown, none 
of the cross sections need be shown for clear under- 
standing. 

The cross sections "G-H" and "J-K" as shown in 
Fig. 118, were not taken from any common center 



BLUE PRINT DRAWINGS 101 



line, because there is no vertical center line in the side 
elevation, as those cross sections were taken from 
created center lines that was desired in showing cross 
sections at these particular points. 






i 

i 


i 
1 








EH 


Wm 






SECTION ON L-M 

L - 


SECTION ON 0-P 



C F 








1 


M 

SIDE ELEVATION 


P 


0. 
R-HENDELEV. 




IS 51 



Fig. 120 

Either one of the cross sections "G-H" or J-K 
could have been placed where the R-H end elevation 
is now placed in Fig. 1 1 8, but in either case, the place 
where that cross sectioned end elevation came from, 
would necessarily be stated below the cross section of 
where it came from. 

The vertical center line of the R-H end elevation 
of Fig. 1 18 did not need the "A" and "B" placed on 
each end as is shown. These were only so used to 
call attention to the part "E" sets in relation to that 
center line "A-B," and likewise the part "F" in rela- 
tion to the center line "C-D" of the blue print drawing 
of Fig. 120. 

What has been explained of Figs. 1 1 7 and 1 1 8 
applies to Figs. 1 1 9 and 1 20 as well. 



102 



HOW TO READ 



COMPLICATED CROSS SECTIONS 

Complicated cross sections are not different in 
meaning from the ordinary cross section, only that it 
is confusing in showing a blue print drawing of a par- 
ticular make up of an article, such as is shown in the 
blue print drawing of Figs. 123 and 125. 




Fig. 121 



Fig. 122 



A complicated R-H end elevation is shown in the 
complete blue print drawing of Fig. 1 23 that was made 
of the object shown in Fig. 121. 

The end elevation of Fig. 123 is a cross section, 
which is taken from the center line "A-B" of the side 
elevation. This center line is the same center line "A- 
B" of Fig. 121, as given in the cross sectioned end of 
Fig. 122. 

The top plan of Fig. 123, shows the outside top 
end shape of the side elevation. 

The value of the cross sectioned end elevation of 
Fig. 123 can be grasped from the perspective drawing 
of Fig. 122. If the end elevation of this were not cross 
sectioned, it would look just like the top plan of Fig. 
123, and likewise, would show the exceptional amount 
of dotted (hidden) lines in a confusing way. 

Many blue print drawings are shown with an end 
elevation of a complicated object, with no cross sec- 
tion, which can be understood with projection lines, 



BLUE PRINT DRAWINGS 



03 



but such a blue print drawing as that of Fig. 1 23 would 
most likely have a cross sectioned end elevation to 
help an understanding, like that shown of the end ele- 
vation of Fig. 123. 

Figure 125 is likewise a complete blue print draw- 
ing of Fig. 124, but taken from the center line "C-D" 



IS ^ M 

mmmMMsm 




TOP CLAN 




Fig. 123 

instead of the line "A-B" of Fig. 121. The center line 
"C-D" of the object is shown in Fig. 124. 

The end elevation of Fig. 125 is also much more 
easily understood than its top plan, because it is a 
cross sectioned end elevation; for the principle of a 
cross section is to show an end elevation drawn to rep- 
resent the center of an object imagined to be cut into 



104 



HOW TO READ 




Fig. 124 



two parts, so that the 
center can be shown 
on a cross section 
without; the outside 
being in front of it. 
If the end eleva- 
tion of Fig. 1 25 were 
not cross sectioned, 
then inside of the 
elevation would be 
drawn with dotted 
lines, like those in 
the top plan. 




BLUE PRINT DRAWINGS 105 

THE WORDS "ELEVATION OR PLAN" ELIMI- 
NATED FROM BLUE PRINT DRAWINGS 

From the beginning of these instructions the words 
"views," "elevations" or "plans" were shown on the 
different blue print drawings as a guide to the reader 
with the explanations of the detail. 

While the words "elevation" or "plan" as used 
were correct, these words are seldom ever shown on 
any blue print drawing, as the reader of a blue print 
drawing should know when looking at an elevation or 
plan that they are such. 

From now on, no more such words as "elevation" 
or "plan" will be shown in the blue print drawing, 
such positions should be fully located by the reader. 

PART VII 

ASSEMBLY BLUE PRINT DRAWINGS 

An assembly blue 
print drawing implies 
from the word "as- 
Fi ff . 126 sembly" — place to- 

gether. 

As practically all objects that are to be made for 
any purpose consist of several parts, each of these 
separate parts when drawn separately are called "de- 
tails," which was dwelt on in the first part of this book. 
When these parts are all placed together, they form an 
assembly blue print drawing as Fig. 1 2 7 shows. 

Figure 126 is a perspective drawing of a Monkey 
Wrench and Fig. 1 2 7 as its assembly blue print draw- 
ing. 

An assembly blue print drawing serves the purpose 
of showing one parts position in relation to that of 
another part, besides showing such parts as are openly 
seen, so that these can be judged for their importance 
as to fit, finish, etc. The assembly blue print drawing 




106 



HOW TO READ 



serves chiefly to show where each piece is to be placed 
in the "assembly." 

The Monkey Wrench of Fig. 126 is a tool that 
every man has handled, and which is easily under- 
stood. Should the blue print drawing of Fig. 127 be 




Fiar. 127 

not readily understood, secure for comparison, a 
Monkey Wrench like the one shown. 

Figure 1 66 shows all of the parts composing the 
assembly blue print drawing of Fig. 12 7, drawn in a 

group, and' explained un- 
der the chapter entitled 
"GROUP DETAIL BLUE 
PRINT DRAWINGS" 
that will be treated in the 
next few pages. 

In Fig. 128 is shown a 
perspective drawing of a 
Machinist's Vise that you 
Fig. 128 no doubt are familiar 

with. Fig. 129 is its assembly blue print drawing. 

Each piece of the Machinist's Vise as composed in 
the assembly blue print drawing of Fig. 129, is drawn 
with separate elevations and a top plan. 




BLUE PRINT DRAWINGS 107 



Each part that it takes to make up the Vise is shown 
in the group blue print drawing of details, as shown in 
Fig. 130. 

When each separate part detail in the group of Fig. 
130 is made up, it should then be assembled, or in 
other words, "put together" from the guidance given 
in the assembly blue print drawing of Fig. 1 29. 

The complete group blue print drawing of details 
of Fig. 1 30, conveys all the information that is neces- 




Fig. 129 

sary for a mechanic in making each part for the Vise 
shown in the assembly blue print drawing of Fig. 129, 
should dimensions be given on each detail. 

In the side elevation of the assembly blue print 
drawing of Fig. 129, what is seen of the inside of the 
vise is shown with dotted lines, because the draftsman 
saw that a cross section was unnecessary to show that 
detail. 

Should the draftsman feel that the inside of the 
Vise did not give as full meaning with the dotted lines 



108 



HOW TO READ 




Fig. 130 

as it would if the side elevation was a cross section, 
(where the use of full lines would be shown inside of 
the Vise), he would perhaps show a cross section in 
the side elevation of Fig. 129 like that of Fig. 131, 
which is given fully in Fig. 1 32. 

Should Fig. 131 be 
applied to the side ele- 
vation of Fig. 129, it 
would be shown as a 
center line cross section 
of the side elevation of 
the Vise as taken from 
the center line "A-B" 
of the L-H. end eleva- 
tion. 

In Fig. 1 33 is shown 

Fis ' 131 the Jaw Body part of 

the Vise drawn with two elevations and a top plan, as 

taken from the group of details of Fig. 1 30, for a blue 

print drawing detail. 




BLUE PRINT DRAWINGS 109 




Fig. 132 



In the side elevation of Fig. 1 33 is shown a broken 
out cross section, which is to show a part of the open- 
ing "C" of the L-H. end elevation that the Sliding Jaw 
is to go into, so that the opening "C" of the L-H. end 
elevation can be partly seen in the side elevation with- 




Fig. 133 

out using altogether dotted (hidden) lines to show 
where that opening is. 

The opening "C" as shown in the side elevation of 
Fig. 133 also shows a part of the hole that is in the 
bottom part of the Body Jaw, open. One half of this 
bottom hole is covered by the outside lower part of 



no 



HOW TO READ 



the Jaw Body, and to get an idea how the broken out 
cross section of the side elevation of Fig. 1 33 really 
looks, follow the dashed arrow line that points in the 
perspective drawing of the Jaw Body of the Vise in 
Fig. 134. 




Fig. 136 

What is shown cross hatched in the broken out 
section of the side elevation of Fig. 133, is on the cen- 
ter line "E-F" of the end elevation where the cross 
section is taken from. The center line "E-F" of Fig. 
1 33 would be the line "G" in Fig. 1 34. 

In the detail of the Sliding Jaw that was shown in 
Fig. 130, and shown separately in Fig. 136; the side 
elevation offers another example of a broken out cross 
section for a blue print drawing. The broken out cross 
section of Fig. 1 36 is taken from the center line "M-N" 
of the end elevation, which can be clearly understood 
by studying the dashed arrow line in the direction of 
the perspective drawing of the Sliding Jaw of Fig. 1 35 
center line "m-n." 



BLUE PRINT DRAWINGS 111 




These two blue print drawings are for the same 
object, the bottom one shows a (broken out) cross 
section; the top one without. Which is the easiest one 
to understand? 




Practice Reading Figures 



112 HOW TO READ 



ENLARGED ASSEMBLY BLUE PRINT DRAWING 

It is often the case in an assembly blue print draw- 
ing, that an actual size drawing would be so small, that 
the necessary detail could hardly be seen. 

Figure 139 would perhaps be the actual size that 
a blue print drawing of a Lever was to give detail to, 
but the draftsman would perhaps make his blue print 
drawing detail the size shown in Fig. 1 40 many times 
larger, so that all of the necessary detail could be 
clearly seen. 

Figure 1 40 is not drawn to full height, as Figs. 1 38 
and 1 39 are. This is shown by the broken left out 
section. Any further detail concerning this broken 
left out section would necessarily be noted in its blue 
print drawing detail. 

In Fig. 1 40, every detail of the Lever as shown 
can be seen to good advantage, while such details can 
hardly be seen in Fig. 1 39 on account of being so 
small. 

When an elevation, as in Fig. 140, is made larger 
than the actual size detail shows, it should have a re- 
mark, such as, "ENLARGED ELEVATION," placed 
below the enlarged elevation as drawn, so as to show 
that what is drawn is more than the actual size. 

If a blue print drawing like that of Fig. 140 be 
desired shown to a Scale, then instead of such a re- 
mark being placed below the elevation as "EN- 
LARGED ELEVATION," the remark would then state 
how many times larger than actual size the elevation 
is, such as "DOUBLE SIZE,"— "SCALE— 6"=4"," 
or whatever the extra size happens to be. 



BLUE PRINT DRAWINGS 113 




Fig. 138 Fig. 139 



Fig. 140 



114 HOW TO READ 



ASSEMBLY CROSS SECTIONS 

In Fig. 142 is shown an assembly blue print draw- 
ing of a Slide with Figs. 141, 143 and 144 to help 
illustrate the explanations, and convey to your mind, 
how two or more pieces when drawn into a complete 
assembly blue print drawing are to be understood 
when an assembly shows a cross section. 

In the end elevation of Fig. 1 42 is shown a cross 
section as taken from the created line "A-B" of the 
side elevation which is noted as such below the cross 
sectioned end elevation. 

When a remark is given below the cross section of 
a blue print drawing, one is to look somewhere in the 
next elevation for a line that the cross section was 
taken from, as for example, "SECTION ON A-B" in 
Fig. 142. In this case, the side elevation has no com- 
mon center line that a cross sectioned end elevation 
could be obtained from, so by placing below the end 
elevation of Fig. 142, such remark as "SECTION ON 
A-B," it is stated where the cross section was taken 
from. 

The line "A-B" of the side elevation of Fig. 1 42 as 
just explained is not considered a natural center line 
of the side elevation, because the center lines are gen- 
erally considered to be the center of a round object, but 
should the line "A-B" be the center line of the side 
elevation of Fig. 1 42, and the cross section as shown 
in the end elevation be taken from this supposed cen- 
ter line "A-B," then the remark "SECTION ON A-B" 
is not needed below the cross sectioned end elevation 
of Fig. 142, as the cross section end elevation could 
then be obtained from the center line "A-B" of the 
side elevation. For example, the cut-in-two section of 
Fig. 141 shows the supposed center line "A-B," which 
is really a created line of the side elevation that the 
cross section is taken on. 

In Fig. 142, the blue print drawing is shown com- 
plete with side and cross sectioned end elevation with 



BLUE PRINT DRAWINGS 115 



its top plan, which shows the Slide with its two Gibs, 
and the Slide Body which are all placed together as 
shown in Fig. 141. 

The cross sectioned end elevation of Fig. 1 42 is 

STCCL GIB 

■SLIDE- 




/ Fig. 141 



o o 

© _€L 

___ ____ 




o o 





Y w/mx% 



Fig. 142 



taken from the created line "A-B" of the side eleva- 
tion. It may be more clearly understood from the 
dashed arrow line that encases the end elevatiton of 
Fig. 142 pointing to the cut-in-two section in Fig. 141. 



116 HOW TO READ 

The Body part, besides that of the two Gibs and 
the Slide are cut-in-two, as all cross sections mean, like 
the cross section of the end elevation of Fig. 142. 

Cross sections are always known by the presence 
of cross hatchings, so one can always understand that 
cross hatching means that the elevation or plan that 
is a cross section is taken somewhere from the eleva- 
tion or plan that is next to the elevation or plan that is 
cross hatched. 

To one who always keeps in mind the meaning of 
the different symbols of materials as Fig. 89 shows, 
which has a general meaning to every one who under- 
stands the reading of blue print drawings, would know 
at a glance what kind of material is being used in the 
different parts cross hatched. Note the cross section 
end elevation shown in Fig. 142. 

There are four separate parts besides the Screws 
shown in the cross sectioned end elevation of Fig. 142, 
which are all to be understood by cross hatchings. 
These either have a different meaning given by the 
material symbols, or the lines of the cross hatchings for 
each part slant in different direction or angle from the 
other, so as to separate the parts from one another. 

The Body part, according to the end elevation of 
Fig. 1 42 is to be cast iron, as shown by the cast iron 
symbol of cross hatching; the Slide and the Gibs are to 
be in steel, as shown by the spacing and design, all 
different from that of cast iron. Each symbol show- 
ing a part slanting in an opposite direction from the 
part that is next to it, is to know the separate parts 
composing the assembly. In this way, an assembly is 
understood for its separate parts by whatever symbol 
or angles the cross hatching shows for each part. 

In Fig. 143 is shown an end elevation almost like 
that of the end elevation of Fig. 1 42, only that the Gib 
is drawn in the cast iron symbol of material, instead of 
steel as was shown for the Gibs of the end elevation 
of Fig. 142. The Gib of Fig. 143 is made in one 
piece, rather than in two pieces as drawn in Fig. 1 42. 



BLUE PRINT DRAWINGS 117 



The purpose of showing the Gib of the end eleva- 
tion of Fig. 1 42 in the symbol of steel, and the Gib of 
the end elevation of Fig. 143 in the symbol of cast 
iron, is to show how the cast iron symbol cross hatch- 
ing for the Gib of Fig. 143 would be cross hatched to 
slant in one direction, while the cast iron symbol of 
Material of the Body part is cross hatched to slant in 
the opposite direction so that the Gib may be known 
from that of the Body as being the same material, but 
separate parts. 




Fig. 143 



Fig. 144 



To know in Fig. 1 42 that the Gib No. 1 is not a 
part of Gib No. 2, is to be able to understand when 
looking at a cross section, that whenever cross hatched 
lines of the same symbol slant in the same direction 
and at the same angle, and are apart from one another 
as shown of the Gibs of Fig. 1 42 ; they are one and 
the same piece connected elsewhere in back of the 
center line that the cross section is drawn. It is not 
always to be figured that they are one, only that this 
is very likely. In order to know, you are to look care- 
fully at every elevation and plan of the blue print 



118 HOW TO READ 



drawing of Fig. 142 for a possible connection of Gib 
No. I, to that of Gib No. 2. 

In both the end elevation and top plan of the blue 
print drawing of Fig. 142, there is no connection of 
Gib No. 1 with the Gib No. 2, which you will notice if 
you study the top plan, and the side and the end ele- 
vation. 

Should the end elevation of Fig. 143 be in place of 
the end elevation of Fig. 1 42, and the slant lines of the 
cross hatched symbol in the same direction on each 
end of the Gib as shown in Fig. 1 43, the Gib would be 
made in one piece by the addition of line which runs 
from "D" to "E." 

The Gib as drawn in the end elevation of Fig. 143 
by connecting the line from "D" to "E" to make it one 
piece, might be like the shape that the perspective cast 
iron Gib shows in Fig. 143. The line "D-E" would be 
what is shown connecting one side of the Gib to the 
other side of the Gib in back of the line "F-G" of the 
perspective cast iron Gib of Fig. 1 43. 

Should the cross section of the Gib of Fig. 143 be 
taken as far back as the broken line "f-g," instead of 
through the line "F-G," of the perspective cast iron 
Gib, the opening part "H" of the Gib would be cross 
hatched in continuation with the same symbol that the 
ends of the Gibs now show, as in Fig. 1 44, and there 
would be no vertical lines that lead from "D" and 
"E" of Fig. 143, as is now seen in the opening "H" of 
the Gib of Fig. 143. 

Should the perspective Gib of Fig. 143 be the Gib 
for Fig. 142, the line "A-B" of the side elevation 
would then be the line "F-G" of the perspective Gib 
of Fig. 143, and the end elevation of Fig. 143 would 
be in place of the end elevation of Fig. 142. 



BLUE PRINT DRAWINGS 119 




Practice Reading Figure 



120 



HOW TO READ 




BLUE PRINT DRAWINGS 121 




122 



HOW TO READ 



In Fig. 1 46 is shown an assembly blue print draw- 
ing of an Engine with a side and an end elevation. 

In the end elevation of Fig. 1 46 are contained a 
half of the front part, with a half of the back part of 
the Engine drawn butted together on the center line. 

The object of a draftsman in drawing the end ele- 
vation with two halves, is to give detail of the front 
and back part of the Engine, so as to convey just 




Fig. 148 



enough information of all that is necessary for an un- 
derstanding of an assembly blue print drawing of Fig. 
1 46 without going to unnecessary work in drawing a 
separate end elevation for the front, and also another 
separate end elevation for the back part of the Engine. 



BLUE PRINT DRAWINGS 123 



As has just been explained, that a half of the back 
end elevation of Fig. 146 is the half of Fig. 147 that 
Fig. 1 48 shows, and the half of the front end eleva- 
tion is the half of Fig. 1 50 that Fig. 1 49 shows. These 
halves are joined together at the center line in the end 
elevation of Fig. 146, so as to show a reasonable 
amount of the front and back part of the Engine in one 
elevation for you to imagine would look. They would 




Fig. 150 



look in reality as in Fig. 1 48 does for Fig. 1 47, and Fig. 
149 for Fig. 150. 

A mechanic who is not familiar with the funda- 
mental principles of reading a blue print drawing, 
would no doubt take his meaning from the end eleva- 



124 HOW TO READ 



tion of Fig. 146, by getting the idea that the Engine 
is drawn fitted up with two Oilers, which is not so. 

By looking carefully at the back end of the Engine 
of Fig. 1 48, one can see only one Oiler in place, which 
is on the left hand side, and when looking at the front 
end of the Engine of Fig. 1 49, that Oiler is on the right 
hand side, because each elevation of each end of the 
Engine is seen from the opposite direction; so that 
when the front and back end elevations that represent 
the halves of Figs. 147 and 1 50 are butted together on 
the center line to form the end elevation of Fig. 146, 
they are apparently two Oilers, although as just ex- 
plained, this is not the case. 

The assembly blue print drawing of the Engine of 
Fig. 1 46, besides what has thus far been explained, 
conveys information for an assembly blue print draw- 
ing without the use of any other elevations or plans, 
for an assembly blue print drawing as given to the 
mechanic is practically to be used only to show the 
general position of the parts, when the several parts 
as composed in the detail blue print drawings are 
placed together. 

In order to understand the assembly blue print 
drawing of Fig. 146 more fully, look at the top plan 
of Fig. 151 as if the same were placed over the side 
elevation and included in the whole blue print drawing 
of Fig. 1 46. 

The full lines as drawn in the top plan of Fig. 1 5 1 
are to show that part of the side elevation that is given 
in Fig. 1 46. The section "Q" that is drawn with 
dashed lines, is that part that was left out to show the 
cross section as seen in the side elevation of Fig. 1 46. 

The section "B" of Fig. 1 5 1 is what was taken out 
of the side elevation of Fig. 146, so as to show more 
of the Timer Lever that projects into the Wheel. Fig. 
1 46 also shows the cross section shape of the Wheel 
in the assembly blue print drawing without the 
mechanics having to look at a separate detail blue 
print drawing of the Wheel for its cross section. 



BLUE PRINT DRAWINGS 125 



What has been explained of the cross section of the 
Engine thus far, can be more simply understood by 
referring to Fig. 145, which clearly sets out for an 
understanding of what the quarter section "Q" of Fig. 
145 shows, as was left out to make the cross section 
as shown of the side elevation of Fig. 146. 

What is shown of the perspective drawing of Fig. 
145 is the impression the mechanic should imagine of 




Fig. 151 

the blue print drawing of Fig. 1 46, after he has given 
the blue print drawing a little study. 

It is well to note that what you have studied in the 
chapters on CROSS SECTIONS, can be materially 
strengthened by studying the cross section of the side 
elevation of Fig. 1 46. This will be known from the 
top plan of Fig. 151, as that which is shown drawn 
with full lines. It shows that the cross section in the 
side elevation of Fig. 1 46 is a quarter cross section, be- 
cause it belongs on two center lines. 

In Fig. 1 5 3 is shown another assembly blue print 
drawing on an Engine that has all of the back end 
only in the end elevation as one elevation. This is not 
like the half elevations as shown in the end elevation 
of the blue print drawing of Fig. 1 46. 



126 



HOW TO READ 



The end elevation of Fig. 153 has more to show 
of the back than could be shown to any advantage for 
the front part of the Engine. 

The cross section as shown in Fig. 1 5 3 is worthy 
of careful consideration and study, so as materially to 
strengthen understanding of an assembly blue print 
drawing. 

In Fig. 1 53, the assembly blue print drawing shows 
only a side and end elevation. To understand the 
cross sections shown for Fig. 153, imagine a top plan 
placed above, as if taken from the side elevation of 
Fig. 153 and like that of Fig. 152. 




Fig. 152 

The cross sections of the Cylinder as seen in the side 
elevation of Fig. 153 is to be known when looking at 
the side elevation as taken from the imaginary top 
plan of Fig. 152. It may be imagined to be like that 
shown in Fig. 1 54. 

It is seen in the imaginary top plan of Fig. 152, 
that the cross section of the side elevation of Fig. 153 



BLUE PRINT DRAWINGS 127 



taken from the lines "A-B-ChD-E," which are the same 
lines "a-b-c-d-e" of Fig. 154. 









niiiili! i! i! i fili! 




^ »g 


iilH 


J 




fO^i^.jAvi^a./- ^-g^'-^ffly 7 ] t| i ! 


^ -W| 


IE 

11 




ipj 


^| 1 




v«/i3 


1 ~"^\ ' 


Ja^f€ 


""^S^^^s 


^^v3 



The lines "A-B" and "C-D" of the top plan of 
Fig. 152 are parallel to each other, thus showing that 
the portion of the top plan of the Engine that fits to 



128 



HOW TO READ 



the line "A-B" of Fig. 152 is on the vertical plane, 
while that which fits to the line "C-D" is on another 
vertical plane. When these two planes are seen in the 
blue print drawing of Fig. 1 5 3, they are seen only on- 
one plane, because the two separate planes are pro- 
jected to the one plane to the side elevation of Fig. 
153 as a cross section, and the only reason why it can 
be seen in the side elevation, is that shown of the 
broken lines "B-O," "M-N" and "P-Q." 

When broken lines as "B- 
O," "M-N" and "P-Q" are 
seen as in the side elevation 
of Fig. 153, they show by 
the cross hatching in the 
cross section, a separation of 
two surfaces not on the same 
plane. The cross section as 
separated with broken lines 
"B-O," "M-N" and "P-Q," 
would necessarily be on two 
planes, as in Fig. 154. 

Figure 1 5 4 also shows 
that the broken lines "B-O," "M-N" and "P-Q" of the 
side elevation of Fig. 153 are on the line "A-B" plane 
of the top plan of Fig. 152. That part of the Cylin- 
der that is separated by the broken lines "B-O," "M- 
N" and "P-Q," is that which is on the center line 
"K-L" plane of Fig. 1 52 top plan of the Engine. 

Any such broken lines as "B-O," "M-N" and "P- 
Q" running through any cross section of any blue print 
drawing similar to that shown in the side elevation of 
Fig. 1 53, shows that what is on one side of the broken 
line is on a different plane from that shown on the 
other side of the broken line/ 

The side elevation of the Cylinder of Fig. 153 is a 
difficult blue print drawing for the average mechanic 
to understand, as a top plan as in Fig. 1 5 2 should have 
been placed above the side elevation and included in 
Fig. 1 5 3 so as to aid the understanding. While such 




Fig. 154 



BLUE PRINT DRAWINGS 129 



a top plan would aid considerably, it is not really 
necessary to one who is versed in the fundamental 
principles of reading blue print drawings, because that 
which is not shown, can be analyzed by giving each 
elevation a thorough study. 

Should it be desired to analyze a cross section of 
the Cylinder of the side elevation of Fig. 153, would 
be to note that the Valve Stem "V" is shown to be 
on a center line of a cross section. 

There is only one Valve 
Stem "V" that can be seen 
in the side elevation of Fig. 
153, which at first glance, 
seems to be on the Engine's 
center line, but is not, as you 
will note when you look at 
the end elevation of Fig. 
153, for the center line "W- 
X" of the end elevation is 
seen as the natural center 
line of the Engine on one 
Fig. 155 si d e f tn e Valve Stem "V." 

Therefore the Valve Stems "V" cannot be on the En- 
gine's natural center line, but must be on another cen- 
ter line as shown in the top plan of Fig. 152, and seen 
in Fig. 154. 

In the end elevation of Fig. 1 5 3, there is shown 
another problem of a cross section which is also to be 
imagined from the top plan provided as in Fig. 156. 

The cross section of the top part of the Cylinder 
in the end elevation of Fig. 1 53 is taken from the cen- 
ter line "W-X," which is the same as the center line 
"W-L" shown in the top plan provided in Fig. 1 56. 

What is shown of the cross section of the end ele- 
vation of Fig. 153 at the top part of the Cylinder 
should be looked for in the top plan of Fig. 156. 
What is shown taken from the part "F-G" of the cen- 
ter line "W-L" as far as "G," and then from "G" as 




130 



HOW TO READ 



far as "H" of the line "G-H," which is the line *'f-g-h" 
of the perspective drawing of Fig. 155. 

The broken out cross section "Z" of the end ele- 
vation of Fig. 1 5 3 must be on a center line, because 
all cross sections are taken from some kind of a center 
line. If you look for the center line "R-S" as shown 
on the top plan provided in Fig. 1 56, you can get the 




Fig. 156 

location of the cross section "Z" in the perspective 
drawing of Fig. 155. 

The cross section "Y" as shown also in the end 
elevation of Fig. 153 is taken from the center line 
"R-S" of the top plan provided in Fig. 1 56, but is not 
shown in the perspective drawing of Fig. 155, because 
it is on the side of Fig. 1 55 that cannot be seen. 

The bottom part of the end elevation of Fig. 153, 
shows an outside half of the Engine, while the other 
half shows a quarter cross section taken out and cross 
sectioned. This cross section is not explained, but left 
to you to solve. The bottom part of the side eleva- 
tion is also left for your study. 



BLUE PRINT DRAWINGS 131 








Bs falH HjpBlIBKiaililili 
llll! 



, ■ c «.i..;..»i«« ) mv-.' 



lfcg-"^t»i*-iTiir,x^» ===^=^i mM t wSS WBIl SI IIU i; 
g|l|wM8S^^gjH|[[||; 



IHiglilP^ 



•J jJ^^x^^^w^X I 




Practice Reading Figure 



132 



HOW TO READ 



HALF ASSEMBLY BLUE PRINT DRAWING 

There are times when a 
blue print drawing shows 
only a half assembly, as 
shown in Fig. 1 60. 

Such half assembly blue 
print drawing, as shown in 
Fig. 1 60, is in principle like 
the half detail blue print 
drawing explained from 
Figs. 79 to 84. 

The half assembly blue 
print drawings are generally 
made to save time, when the draftsman is in haste, or 
has only one to make up, and needs no full blue print 
drawing for future use. 




Fig. 157 




Fig. 159 



Fig. 158 



Figure 1 60 gives all necessary information of the 
design. 

When such words as "HALF DETAIL* * or "HALF 
ASSEMBLY" are given below in an assembly blue 
print drawing, they suggest that only one half is drawn, 



BLUE PRINT DRAWINGS 133 



and that the other half is to be imagined just as that 
drawn in Fig. 1 60, and realized with the dashed lines 
that the half assembly of Fig. 1 6 1 shows. 




Fig. 160 




Fig. 161 



What is seen in the cross sectioned half assembly 
blue print drawing of Fig. I 60 can be understood from 
Figs. 15 7, 158 and 159. 

Figure 1 59 represents what is seen of the L-H. end 
elevation of Fig. 1 60 as on the center line of Fig. 1 58. 



134 



HOW TO READ 



PART VIII 
GROUP DETAIL BLUE PRINT DRAWINGS 

In Fig. 1 66, there are several separate detail parts 
all drawn in one group blue print drawing. Each de- 
tail in this group must be studied apart from the others 
shown, so that each will be understood. 

The object of giving so many details in one group 
is to remove the necessity of making a separate blue 
print drawing detail of each part. Another reason is 




Fig. 166 

that all the parts may be before the mechanic so that 
the mechanic does not have to scout through several 
blue print drawing details before he can find the detail 
that he wants. 

A disadvantage of a group detail blue print draw- 
ing as shown in Fig. 1 66 is that, should there be only 
one blue print drawing furnished, only one mechanic 
could conveniently use it at a time. This would not 
allow the free use of same without interference of the 



BLUE PRINT DRAWINGS 135 

other mechanics, should they be working on the other 
part of the group at the same time. 




136 



HOW TO READ 



The group of details as shown drawn in Fig. 1 66 for 
each separate part of the Monkey Wrench, as that 
encased with a dashed arrow line, may be understood 
from the perspective drawings of Figs. 162, 163, 164, 
165, 167, 168 and 169. 

In Fig. 1 70 is a group of details containing remarks 
about the parts; as is true of the general run of all blue 
print drawings. The group of details of Fig. 1 70, is 
for study, without any perspective drawing as was used 
in the other explanations of this book, to show what 
each part is like. 




Fig. 171 

The group of details of Fig. 1 70, is left to you for 
study and practice reading. 

Figure 1 70 is a typical blue print drawing, giving 
place between the dimension arrows for the sizes, and 
the general remarks that are always shown of a detail. 



Another group detail blue print drawing is sh< 

in Fig. 1 30, as well as on page 1 19. 



BLUE PRINT DRAWINGS 137 



SEPARATE DETAIL BLUE PRINT DRAWINGS 

The blue print drawings of Figs. 1 7 1 and 1 72 are 
used to show separately, the details as composed in 
either of the blue print drawings, and likewise have no 
perspective drawing to help the reader to an under- 
standing, but left for you to study for their meaning. 




Fig. 172 

The separate blue print drawing details as shown 
in Figs. 1 7 1 and 1 72 may be composed from one to 
many more elevations and plans, all depending upon 
what the blue print drawing is to show. 



It may be to your interest to know that Figs. 1 70, 
1 7 1 and 1 72 were taken from the assembly blue print 
drawing of the Engine of Fig. 1 53. 



138 



HOW TO READ 



DIAGRAM BLUE PRINT DRAWINGS 

In Fig. 1 74 is shown a diagram blue print drawing 

for the wiring of a Gasoline Engine provided with 
electric wires for the electric spark. 




Fig. 173 



The diagram blue print drawing of the Engine of 
Fig. 1 74, is the proper way of showing how the wires 
are to be connected. 



You will note that the center Lever "S" of the 
Engine of Fig. 1 74, is drawn with full lines, and that 
the two Levers as shown with the letter "T" are drawn 



BLUE PRINT DRAWINGS 139 



with dashed lines. These two Levers "T" drawn with 
dashed lines are to show the limit of the swinging posi- 
tions that the full drawn line Lever "S" can be placed 
in, and not, as they might seem to show, that they are 
three Levers. 

Figure 1 73 gives a good understanding of the wir- 
ing as shown in the blue print drawing of Fig. 1 74. 




Fig. 174 



GEAR BLUE PRINT DRAWINGS 



Blue print drawings of Gearing are quite simple to 
understand and, providing that you understand the 
principles of projection of elevations and plans as 
treated in the first part of this book. 



140 



HOW TO READ 



The object of showing blue print drawings of Gear- 
ing is to show the principles of teeth as drawn on same. 

It is not necessary to explain in this book any 
remark given on a blue print drawing of any kind of 
a Gear which relates to the mechanical design and 
usage. Such remarks are understood as part of the 
trade of the mechanic who has anything to do with 
Gears. 



SPUR GEAR BLUE PRING DRAWING. 

Figure 1 75 shows a per- 
spective drawing of two 
Spur Gears in mesh for an 
easier understanding of 
the blue print drawing of 
Fig. 176. 

A blue print drawing of 
a Gear usually shows a 
few teeth drawn in the 
outer rim, as marked with 
the letter "T," as in 
Fig. 176. 

It was not necessary for 

a draftsman to draw all 

the teeth around the rim 

Fig. 175 on the side elevation of 

Fig. 1 76, because showing 

all the teeth would only make drawing nice to look at. 

Nothing more would be shown of the Gear than is 

shown by the few teeth with the letter **T." 

Even the few teeth shown with the letter "T" in 
the side elevation of Fig. 1 76 are not necessary on a 
blue print drawing of a Gear, because with the pitch 
circle drawn, besides other marks or words, such as 
"P.D." after the pitch diameter, the diametral pitch, 
etc., that are usually on a blue print drawing, there is 
enough information to know that the drawing is a 
Gear. 




BLUE PRINT DRAWINGS 141 




Fig. 176 

Another reason why no teeth need be drawn to 
show that a blue print drawing is a Gear, is that there 
would be such information in the form of reading mat- 
ter on a blue print drawing to show that it is a Gear, 
such information as "80 TEETH"— "14 PITCH," and 
possibly the circular pitch, given in Fig. 1 76 along with 
other words. 



The tooth profile as shown in Fig. 1 76 blue print 
drawing of the Gear, need not necessarily be given, 
but such information always adds considerably to the 
understanding whenever shown. 

The end elevation of Fig. 1 76 need only show with 
straight lines where the teeth are to be. No actual 
teeth need be shown, as is shown with the letter "T" 
in the side elevation. 



142 



HOW TO READ 



SPIRAL GEAR BLUE PRINT DRAWING. 




Fig. 177 



Figure 1 78 is a blue print 
drawing of Fig. 177 that 
shows a set of Spiral Gears. 

What has been explained of 
Spur Gears may be said df 
Spiral Gears. 

The slant lines "S" of the 
Spiral Gear blue print drawing 
of Fig. 1 78 suggests the loca- 
tion of the teeth, like in the 
Spur Gear blue print drawing 
of Fig. 1 76. 




Figr. 178 



BLUE PRINT DRAWINGS 143 



BEVEL GEAR BLUE PRINT DRAWINGS. 

Figure 1 79 shows a perspective drawing of two 
Bevel Gears in mesh, which when drawn as a part of 




Fig. 179 




Fig. 180 

an assembly blue print drawing, could be like that 
of Fig. 180. 

In the blue print drawing of Fig. 180, there is 
but little information given of the shape of the Gear 



144 



HOW TO READ 



drawn. What is given is sufficient for the purpose 
of showing the Gear located in a portion of an assem- 
bly blue print drawing. 




Quite often a pair of Bevel Gears are only partly 
cross sectioned, and partly drawn to represent as they 
actually look, like the blue print drawing of Fig. 1 82 
representing the Gears as shown in Fig. 181. 




Fig. 182 



BLUE PRINT DRAWINGS 145 



A blue print drawing, such as that in Fig. 182, 
providing no dimensions are needed, offers two ways 
for the mechanic using blue print drawings to under- 
stand 




Fig. 183 

For a detail of the pair of Bevel Gears shown in 
Fig. 183, a blue print drawing like that in Fig. 184 is 
the most common and practical way. In Fig. 1 84, 
details of the two Bevel Gears are shown by the use of 
a cross section in the blue print drawing, to which 
dimensions can be easily applied. 




Fig. 184 



146 



HOW TO READ 



WORM GEAR BLUE PRINT DRAWING. 

Figure 186 is a 
blue print drawing of 
the Worm and the 
Worm Gear shown 
in the perspective 
drawing of Fig. 185. 
The end elevation 
of Fig. 1 86 shows in 
the bottom half, the 
slanted position of 
the teeth of the 
Worm Gear, besides 
the quarter cross sec- 
tion of the upper 
lg ' half, while the side 

elevation of Fig. 1 86, shows a broken out cross section 
of a part of the Worm and the Worm Gear, easily 
understood by looking at Fig. 185. 





Fig. 186 



BLUE PRINT DRAWINGS 147 



MOVEMENT OF TRAVEL IN ASSEMBLY BLUE 

PRINT DRAWINGS. 

In Fig. 187 is shown the movement of travel of 
a Governor so as to represent on a blue print drawing 
the path of travel and the limit of space such move- 
ment occupies. 




Figr. 187 

Such movement of travel is practically only shown 
in an assembly blue print drawing with dotted lines, 
as is shown in Figs. 1 74 and 187. 

Sometimes the movement of travel is shown with 
the center lines only, and not with dotted lines out- 
lining the shape of the part traveled. 

The distance of any movement of travel is meas- 
ured between center lines on the center of the arc or 
path of travel. 



148 HOW TO READ 



PART IX 

CONVENTIONS 

Conventions when applied to the reading of a blue 
print drawing is the necessary words or symbols to 
further a complete understanding of the blue print 
drawing. 

Practically every blue print drawing contains con- 
ventions in some form, which are to be understood 
as a part of the actual drawing. 

A convention may be more fully understood as a 
particular mark, word, design, symbol or sign which 
has a general meaning as adopted in the science of blue 
print drawing, which when seen, is to be understood 
for its full meaning. 

The following symbols, letters or words when ap- 
pearing on a blue print drawing are called conventions. 

MATERIAL MARKS 

This chapter explains the conventions of materials 
shown with initials on a blue print drawing, are also 
the symbols of materials as shown in Fig. 89. If no 
initials are used to show what the material is, then the 
full name is shown on the blue print drawing. Such 
initials and their meanings are as follows: 

C.I. means Cast iron. 

C.S. means Cast steel. 

C.R.S. means Cold rolled steel. 

Cp. means Copper. 

W.I. means Wrought iron. 

Mai. means Malleable iron. 

Br. means Brass. 

T.S. means Tool steel. 

H.S.S. means High Speed steel. 

Alum, means Aluminum. 



BLUE PRINT DRAWINGS 149 



SCALES 

In the making of anything from a blue print draw- 
ing, it is understood that the blue print drawing as a 
general rule is drawn to a scale or stated size. Should 
the article to be drawn be not too large, and if it can 
be drawn on a moderate size sheet, a full size scale is 
almost always used, and such is to be stated in the blue 
print drawing as "SCALE— FULL SIZE" or "SCALE 
— 12" = IV Whatever the desired scale may be, it 
is to be stated on the drawing. 

Should a very large article, such as a Steam Roller 
or any of its large parts have a drawing, such a draw- 
ing could not be conveniently made to full size, there- 
fore a scale of considerable reduction would be shown, 
such as "SCALE — 12" — 1"," etc., meaning that every 
inch in length, width or height drawn with such a scale 
would represent one foot. 

There are many scales that can be used in the 
making of a blue print drawing, all depending upon 
the relation of the size of the part to be made, to the 
size of the drawing sheet used. 

The following scales are most commonly used, al- 
though there are scales other than those listed here 
that are used: 



6" 


=i 


means 


1/2 


size 


H' 


'=1 


' means 1/16 


size 


4" 


=i 


means 


1/3 


size 


'/ 2 "=1 


' means 1/24 


size 


3" 


=r 


means 


1/4 


size 


%' 


'=1 


' means 1/32 


size 


2" 


=i' 


means 


1/6 


size 


%' 


= 1 


means 1 /48 


size 


\y?' 


'— i 


means 


1/8 


size 


%' 


'=1 


' means 1/96 


size 


\"~ 


=i 


means 


1/12 


size 


1 " 
i r; 


= 1' 


means 1/192 


size 



WTien an article to be drawn is very small in actual 
size, an enlarged scale is generally used so as to show 
everything much larger than it actuallv is, so that ease 
and accuracy can be used by the draftsman in the 
making of such drawing, therefore a scale such as 
"DOUBLE SIZE," "SCALE— 6"— 1"," etc., would be 
used in the making of such drawing. 



150 HOW TO READ 



Practically every blue print drawing is made to a 
scale, and whatever scale is used is most generally 
stated on some part of the drawing. 

Sometimes a scale is not noted on a blue print 
drawing, so as not to permit any freedom in taking 
dimensions from the drawing. Should a dimension be 
omitted or will not check up, it is always advisable to 
take up such matters with those who are responsible 
for such drawings. 

In almost any blue print drawing, even when the 
design is practically finished, a minor change may be 
necessary. Such a change may be taken care of mostly 
in dimensions. The mechanic should not scale such 
a drawing. For this reason, almost all blue print 
drawings show the words "DO NOT SCALE." 

Whenever the words "DO NOT SCALE" are 
shown on a blue print drawing, never measure any 
dimension from the drawing, but go only by whatever 
dimensions are shown. 

Another reason why the "DO NOT SCALE" is so 
often shown on a blue print drawing is because of 
the inaccuracy of the drawing due to shrinkages and 
stretching of the drawing when several days have been 
required to make it. Such conditions are taken care 
of, and allowances made in the draftsman's calcula- 
tions when he states the dimensions on the blue print 
drawing. 

MARKS 

f means This mark on any surface drawn is to 
show that the surface is to be machined, in other 
words, to finish smooth, as Fig. 1 88 shows. 

ff means To be finished extra smooth. When the 
initials F.A.O. is used, no f need be shown. 

F.A.O means To finish all over. 

G. means To grind. 



BLUE PRINT DRAWINGS 151 



GEARING MARKS 

P.D. means Pitch diameter. 

D.P. means Diametrical pitch. 

O.D. means Outside diameter. 

R.D. means Root diameter. 

C.P. means Circular pitch. 

C. means Clearance. 
C. to C. means Center to center. 

PATTERN NUMBERS 

PATT. means Pattern number. 

When a number is shown such as PATT. K- 1 2 or 
PATT. 1933-C-22, on a blue print drawing, it is to be 
understood that a particular method is used in marking 
the pattern for record keeping. 

PATT. K- 1 2 is a number applied to a pattern, in 
which the letter "K" shows the series, and the figure 
"12,** is the order in which it belongs. 

PATT. 1933-K-22 would show that the figure 
"1933" would be the blue print drawing number, the 
letter "C," the size of the drawing, and the figure "22" 
would be the twenty-second detail of the drawing 
"1933." The pattern number would be the same as 
the drawing number for one record to keep tab of. 

CROSS HATCHINGS 

Any cross hatching of any blue print drawing is a 
convention, because it is used to give a general under- 
standing among the readers of blue print drawings. 

In Fig. 1 88 is shown a five spoked Hand Wheel, 
with an R-H. and a L-H. end elevation to its side 
elevation. 

As previously stated in the first part of this book, 
only one of the end elevations was needed as a pro- 
jection from the side elevation; but in Fig. 188, the 
using of both, the R-H. and the L-H. end elevations 
in the same drawing is only to show by contrast the 



152 



HOW TO READ 



effect of a practical projection in relation to its theo- 
retical projection. 

The R-H. end elevation of Fig. 1 88 is the theoret- 
ical projection from the side elevation of what is seen 
of the spoke below the center line "A-B" when such 
spoke does not completely appear on the center line 
"C-D." 

Leading authorities claim and always show on their 
drawings, that when a spoke of a Wheel is not corn- 




Fig. 188 

pletely on the vertical center line of the side elevation, 
that such spoke is to be projected as a center line pro- 
jection, as the L-H. end elevation shows, and not as 
the R-H. end elevation shows. 

The writer cannot understand, nor has ever been 
able to find out the "WHY" of this so-called practical 
spoke projection, which applies only to the projection 
of spokes, but knowing its general use, imparts to you 
the condition as it exists. 



BLUE PRINT DRAWINGS 153 

Such a blue print drawing of Fig. 188 requires 
only one end elevation, and such end elevation would 
no doubt be as the L-H. end elevation shows, although 
there are many end elevations of the spoke as the 
R-H. end elevation shows. 

Ordinarily, such a cross section as shown in the 
L-H. end elevation of Fig. 188 would be considered a 
zig zag cross section taken from the line "C-E-F" of 
the side elevation, which would also have the words 
stated below the L-H. end elevation stating such. 




Fig. 189 




Fig. 190 



Many articles are drawn with only one elevation. 
To show its other elevation, requires only a cross 
section of whatever shape it may be, cross hatched 
somewhere inside of the same, as is shown with Figs. 
189 and 190. 



154 HOW TO READ 

LINES 

Lines of blue print drawings are made with various 
meanings, which are as follows: 

Full lines 

For all outlines of an article as drawn. 

Invisible, dotted or hidden line. 

The invisible or hidden line is commonly called 
the dotted line which is used in a blue print drawing 
wherever there is a line hidden. Such an invisible or 
hidden line is also used to show the movement of 
travel of parts, as is shown in Figs. 1 74 and 187. 



Center line 



Dimension or extension line. 

The use of dimension lines as shown, is rarely ever 
used, for the regular medium line with arrows placed 
on each end is what is almost always used. 

The above line is practically used only as an ex- 
tension line. 

CENTER LINES 

Practically every blue print drawing has one or 
more center lines, which are used to show the centers 
of an article. 

Should an article drawn have two or more center 
lines, then such center lines show each center construc- 
tion of the most particular part to work to, as almost 
all of the important dimensions are taken from a cen- 
ter to center measurement. 

Holes are always measured between center lines 
which show the center to center dimension. 

Whenever such letters as "C to C." are shown on 
a blue print drawing, they are to be understood as the 
center to center of center lines. 



BLUE PRINT DRAWINGS 155 

Such symbol as this appearing on a line 
always means center line. 

DIRECTIONS 



Figr. 191 




Fig. 192 



Fig-. 193 

Straight direction arrow = as Fig. 1 9 1 shows. 
Centrifugal direction arrow = as Fig. 1 92 shows. 
Both directions arrows == as Fig. 193 shows. 



DIMENSIONS 

Dia. means diameter. 

The letter"R" of Fig. 1 94 means radius when 
shown after a dimension, and is inside of an arrow 
line. It shows that the dimension is measured from 
the center of a circle or arc to its outside edge, on the 
blue print drawing, as in Fig. 197. 




y 



A 



Fir. 19S 



A*' 



Figure 195 shows a radius dimension, explanation 
of which is the same as the above, only that it is 
folded. The idea of such a folded radius line is to 
show that the actual center is in a straight line from 
the straight part of the arrow line that the dimension 
is to be measured from. The reason why the actual 
center is not shown in its place, is to make room for 
other details that can be drawn in its place. By 
folding the radius arrow line, such condition can be 
provided for. Such a radius arrow line is shown in 

Fig. 176. 



56 



HOW TO READ 



12.875 



+.005 
—.003 



When such fractional dimensions as given above 
are shown in decimals after a whole number and deci- 
mal, it is understood that the allowable variations of 
the dimension is not to be over five thousandths inch 
oversize, or three thousandths inch undersize. The 
arrangement of the above dimension can be in any 
combination other than that shown. 





*!♦ '/Z DRILL- 2 HOLES 




u,ij 


i Y 


« 


-4" 




-+ 12" *- 









Fig. 196 

When two or more dimensions are seen between 
the same limit, they are to show that there are as many 
sizes to be made as there are dimensions, as in Fig. 
196. 



DIMENSION CHANGES 

Practically every blue print drawing, after being 
in use a little while requires dimension changes to meet 
new conditions. 

When a dimension change is required, it is gen- 
erally the practice of draftsmen to erase the dimension 
figures and insert in their place a capital letter inclosed 
in a circle, and whatever letter is used refers to the 
change column of the drawing, showing what the di- 



BLUE PRINT DRAWINGS 157 



mension was, what it is now to be, the date that such 
a change was made, the authority of the change, and 
any other necessary remarks. Such change column 
would be somewhat like Fig. 197. 

Any change in the design, other than dimensions 
or remarks would necessarily require a new drawing, 
and such would not come in the scope of the reader 
of the blue print drawing. 



TITLE BLOCKS 

Practically every blue print drawing has a title 
block somewhere in the drawing, and most generally 
on the lower right hand corner, as in Fig. 1 9 7. 

Inside of the title block is all the information that 
is required of those responsible for the drawing. This 
information is rarely of much use to the general reader 
of the blue print drawing, except for the name of the 
article drawn, the scale used, and possibly the date 
when the drawing was made. 

Scales are seldom ever placed inside of the title 
block of a group detail, for the reason that the draw- 
ing may have several different scales to show for each 
detail, which would make it impossible to state con- 
veniently the scale in the small space allowed, there- 
fore each detail in a group of details generally shows 
the scale placed somewhere below the detail as drawn. 

In every separate detail blue print drawing, the 
scale is generally shown in the title block as in Fig. 197. 

All of the blue print drawing in this book, except 
Fig. 197, have no title block, for it was not necessary 
to consider such in the educational problems dwelt 
with. 



158 HOW TO READ 



BILL OF MATERIAL 

In every blue print drawing, there is some sort of 
material such as Screws, Taper Pins, Babbit, etc., 
needed for the completion of the article drawn, and 
such material is usually, but not always, listed in the 
upper right hand corner of the blue print drawing. 
Such list of material is called a bill of material, as in 
Fig. 197. 

In assembling all of the details of an article, there 
is material such as Grease Cups, Gauges, etc., required 
for use then, and not when the detail is being made 
up. In order that all of the miscellaneous materials 
may be ordered and kept in readiness until needed, a 
separate assembly bill of material is almost always 
made up for such conditions. 

In Fig. 197, the bill of material gives in the column, 
only one article that is needed for the detail to be 
made. Should any other material be needed, a place 
is provided for the same. 



SPECIAL SECTION DETAIL 

When any blue print drawing is made small, and 
a particular part of such a drawing has enough im- 
portance attached to it, such particular part may be 
extended out from the detail of the part, as in Fig. 197. 

There are two special section details in Fig. 197, 
the upper one is to show the dimension of the sfot 
without showing a whole top plan, while the lower one 
is an extended out cross section drawn double size to 
show the ribs, and where the web is recessed for a 
clearer view. 



BLUE PRINT DRAWINGS 159 



POSITIONS 

In detail blue print drawings, it is advisable for 
draftsmen to show positions in dashed lines, such as 
the end of the Rod, the Key and the other half of the 
Eccentric Strap, as in Fig. 197. 

The showing of positions in Fig. 197 offers the 
reader of the blue print drawing an understanding of 
the actual detail that is to be made up by being drawn 
in full lines, while the relation of the detail is shown for 
its position with the other details that it is placed with. 




Fig. 197 

Other blue print drawings are made for the detail 
of the positions, which in Fig. 197 is shown with the 
words "SEE DETAIL C-21," _"C-23," — "E-24" 
and "E-25." 

The Key as shown cross hatched in Fig. 197 is in 
its natural position according to its end elevation pro- 
jection, but when shown as it is with dashed lines in 
an upright position at 90° to its actual projection, a 
clearer understanding of the whole Key is gained for 
its position. 



160 



HOW TO READ 



BREAKS 

Breaks in a blue print drawing of Shafts and Rods 
are always used to show what is left out, so as to 
shorten the actual drawing of same. 




Fig. 198 




Fig. 199 



Fig. 200 



Whenever a Shaft or Rod is shown broken, the 
break is made with irregular lines to give an idea of 
the shape, as in Fig. 198, 199 and 200. To show a 
break in other articles drawn, the same principle is 
used. 



BLUE PRINT DRAWINGS 161 



NUT PROJECTIONS 

When Nuts are shown in an elevation, they appear 
according to the position they happen to occupy in 
the drawing as in Figs. 206 to 210. 

The dotted lines showing the hole, and the dotted 
lines showing the thread, are seldom ever shown for a 
Nut of Fig. 206, when such a Nut is drawn with an- 
other article, because the shape as drawn shows that 
it is a Nut. Figure 207 might be drawn to show the 
hole, because there is little to indicate that it is a Nut. 




Fig. 201 Fig. 202 Fig. 203 Fig. 204 



Fig. 205 




Fig. 206 



207 



Fig. 208 



Fig. 209 



Fig. 210 



It is not likely that Fig. 207 would ever be drawn 
to show a square Nut in a blue print drawing, for Fig. 
206 may better indicate a square Nut. 

Figure 206 shows a square Nut, while Fig. 208 
shows a hex Nut which look considerably alike, but 
you will note in Fig. 206 that the square Nut is much 
wider than the hex Nut in Fig. 208. Further, the 
square Nut is considerably thinner than the hex Nut. 

A castelated Nut of Fig. 205 and 210, is usually 
hexagonal, in order that its six sides may allow more 
slots for the alignment of the Cotter Pin, thru the 
Cotter Pin hole of the thread. 

No standard Nut should ever be cross sectioned; it 
should always be drawn as a whole Nut. 



162 HOW TO READ 



SCREWS, HEADS AND THREADS 

The heads of Screws are to be understood in the 
same manner as explained of Nuts, only that the width 
of Screw Heads is not as great as that of their Nuts. 

Standard Screws and Heads, like Nuts are always 
drawn as a whole and never cross sectioned. 

Screw threads, whether they are on a Screw, Stud, 
Rod or Bolt, are all drawn to convey the same 
meaning. 

Any conventional method of showing threads can 
be used wherever a thread is to be drawn, as all 
threads as shown convey the same meaning. Con- 




Fig. 211 Fig. 212 Fig. 213 Fig. 214 Fig. 215 

ventional methods of showing threads are shown in 
Figs. 211, 212, and 213. 

The method shown in Fig. 213 is the one used 
mostly by tool designers, but is rarely ever seen in a 
machine drawing. 

All threads in Figs. 211, 212, and 2 1 3 are under- 
stood as being a Single United States Standard 
Thread, and should a double, triple or quadruple or 
as wanted, such threads would be drawn with a larger 
angle as shown in Fig. 2 1 4, and with a note to state 
such a condition. 

When U.S.F. is shown for a thread it means United 
States Standard Form Thread. All other single 
threads are understood to be the "V" shape. 

Fig. 2 1 5 shows the angle direction of the thread 
to be in the opposite direction for a left hand thread. 



BLUE PRINT DRAWINGS 163 



TAPPED HOLES 

The full drawn circle with a dotted outer circle as 
in the top plan of the hole going thru the special Nut 
of Figs. 2 1 6 and 2 1 7 shows the proper way of indi- 
cating a tapped hole. 

Some leading authorities show in their drawings, 
a full line circle, with an outer full line circle drawn 
to about 45°, or a little past the quadrant of the two 
center lines to represent a tapped hole as in the top 
plan of Fig. 2 1 8. This should be borne in mind. 




Fig. 216 



Fig. 218 Fig. 219 



Should the tapped hole of the Nut not go thru, 
as in Fig. 2 1 9, then the inside, as well as the outside 
circles are both drawn dotted in the top plan to show 
a hidden tapped hole. 

Either one of the elevations of Figs. 216, 217 and 
218, is given as a correct way of showing a tapped 
hole. Figure 2 1 6 is the full cross section, Fig. 217a 
quarter cross section, while the elevations of Figs. 2 1 8 
and 2 1 9 show the hidden method. 

Should the threads in question be left handed in- 
stead of right handed as they are now shown, then 
the angles of both, the Screw thread and the hole 
thread are shown reversed. 

When a Screw thread is shown not to occupy the 
whole depth of the tapped hole as in Fig. 220, the 



164 



HOW TO READ 




Fig. 220 

angle lines showing the thread of the Screw are drawn 
as it should be shown, and the lines to show the 
thread of the hole are drawn to the opposite angle. 

CORED HOLES 

Whenever a remark as "core" is given on a blue 
print drawing, such remark means that the article to 
be made is first cast in a foundry and left as it is, or 
to be finished in a machine shop. Whatever the 
shape of the core, the casting will show a hole of that 
shape, to be either left as it is mounded, or other re- 
marks will show where it is to be finished. 

Should the cored hole be required to be finished, 
such cored hole is used to relieve excessive metal in 
machining. 

The cored holes are noted in the blue print draw- 
ing of Fig. 22 1. 



GROUPED HOLES 

When there are several holes grouped closely to- 
gether, or in uniform location about the article, it is 
not necessary to state the sizes and given remarks for 
each hole, for a blanket note may be used, especially 



BLUE PRINT DRAWINGS 165 




Figr. 221 

if each class of hole is noticeably of the same size, as 
in the blue print drawing of Fig. 221. 



BEARINGS 



Figure 222 shows the torn out part of a blue print 
drawing of an Emery Wheel Arbor and gives the 
meaning of the Shaft marked with criss cross lines. 




Figr. 222 

The criss cross lines of the shaft of the Arbor as is 
shown with the letter "C" in the blue print drawing of 
Fig. 222, is to indicate that what is criss crossed is to 
be understood as the space occupied by a Bearing. 



166 HOW TO READ 



EFFECTS OF SHADING 

The effect of shading is not really necessary in any 
blue print drawing, but its use, if properly drawn, 
helps to make the meaning clearer, besides placing an 
artistic touch to whatever is shaded. The theory of 




Fig. 223 

shading is the effect of lights and shadows cast upon 
an article to show its perspective. 

Shading is most forcefully shown in round surfaces. 
Flat surfaces as shown in the end of Fig. 223 may be 
shaded to give the necessary contrast, showing that 
the surface is flat. 

Figure 223 shows the round part of the Shaft 

spaced with broken lines, as the light projects from 

the equal imaginary spacings of its end, while the flat 

surface of the end is shaded to show the lights cast 

on its end. 

The only real practical place to show shading is in 
an assembly blue print drawing, because of the artistic 
value it gives the drawing of the complete article, for 
shading always adds considerable weight for its ac- 
ceptance by those concerned. 

It is always a poor practice for shading to be shown 
in a detail blue print drawing, because shading lines 
confuse dimensions, while in assembly blue print draw- 
ings, dimensions are very rarely ever shown, and what- 



BLUE PRINT DRAWINGS 167 

ever dimensions are shown, would be only for the 
principal dimensions, such as, over all, center to cen- 
ter dimensions, etc. 

HOW A BLUE PRINT DRAWING IS MADE 

A blue print drawing is made on the same prin- 
ciple as a photograph is printed. 

A photograph is printed from a plate or film talcen 
by a camera, while a blue print drawing is printed 
from a tracing cloth drawing made by a draftsman, 
and such a tracing cloth drawing is much like a film 
for results obtained. 

A tracing cloth drawing is cloth prepared with a 
glazed surface to hold ink, and its transparency en- 
ables the draftsman to draw his design, dimensions, 
remarks, etc., with ink from over the original rough 
pencil drawing on paper. Such a tracing cloth draw- 
ing is usually referred to as a tracing. 

A tracing is as flexible and transparent as a film, 
and a blue print drawing is printed in the same man- 
ner as a photograph, that is why a blue print drawing 
is called a "blue print" 

Blue print drawings are almost always printed on 
paper because of its cheapness, although in cases where 
there is hard usage of said blue print drawings, they 
may be printed on blue print cloth, which is more 
expensive. 

Before a blue print drawing can be made, a sheet 
of dry paper or cloth that has been previously pre- 
pared with chemicals, white to all appearances when 



168 HOWTOREAD 



no strong light is about, is placed under the bracing 
and firmly held together under a plate of glass which 
acts as a clamp when secured in a frame. It is then 
exposed to a strong light for a certain length of time. 

As the light penetrates thru the transparency of 
the tracing, it turns the chemically prepared paper 
underneath to be blue, except the places where there 
are ink lines or letters on the tracing, which will remain 
white on account of the light not being able to pene- 
trate thru such black ink lines. 

When such chemically prepared paper has been 
exposed long enough to a strong light to turn the paper 
blue wherever there is no ink lines, then such paper 
is taken out from underneath the tracing and placed 
in water to wash away the chemicals, especially where 
the ink lines of the tracing did not let the light turn 
the paper blue. 

After the paper has been thoroughly washed of 
all chemicals, it is then hung up to dry and is soon 
ready for use. 

Thru repeated operations, as many blue print 
drawings copies may be obtained as are desired. 

A tracing offers a permanent record, and with the 
considerable amount of labor placed on the same, if 
properly handled, should last a life time. The per- 
manent tracing would be closely guarded from fire 
or theft. 

Blue print drawings for tool and other designs that 
are practically used but once, are drawn with pencil 
on a tracing paper called VELLUM, and blue prints 
printed from same, show faint white lines on the blue 
print drawing, on account of the transparency that 
allowed the light to penetrate thru the pencil lines of 
the vellum tracing. ~ 



BLUE PRINT DRAWINGS 169 



CONCLUSION 

In conclusion, it is hoped that this work will fulfill 
its aim, that it will explain "HOW TO UNDERSTAND 
BLUE PRINT DRAWINGS." 

It is urged upon you to re-read this book every 
few weeks, until the fundamental principles stand out 
in your mind as never to be forgotten. Master the 
principles so thoroughly that whenever any kind of a 
blue print drawing is at hand, no matter how compli- 
cated, a complete understanding can be had with but 
little study. 

Suggestions and criticisms for the betterment of 
this book will be welcome, so that the next edition 
may be strengthened to meet every demand of those 
who are working for skill in the reading of blue print 
drawings. 



